Russia’s invasion of Ukraine entered its sixth day on Tuesday, with a huge convoy of Russian tanks and armored vehicles inching closer to the capital of Kyiv and fighting intensifying there and in other big cities.

Russia stepped up shelling of Ukraine’s second-largest city, Kharkiv, and pounded several civilian buildings. More than 70 Ukrainian soldiers were reportedly killed when Russian artillery hit a military base in Okhtyrka, a city of about 50,000 people between Kharkiv and Kyiv.

The Russian economy is paying a price for the invasion, with Western sanctions causing the ruble to tumble and restricting the country’s use of its huge foreign currency reserves.

Here’s a look at things to know about the Russia-Ukraine conflict.

WHAT’S HAPPENING ON THE FRONT LINES?

Russian shelling struck central Kharkiv’s Freedom Square just after sunrise Tuesday, badly damaging a regional administration building and some other structures, and killing at least six people and injuring dozens of others, Ukrainian officials said.

It was the first time the Russian military hit the center of the city of 1.5 million people, though shells have been hitting residential neighborhoods in Kharkiv for days.

Ukrainian President Volodymyr Zelenskyy called the attack “frank, undisguised terror,” blaming a Russian missile and calling it a war crime. “Nobody will forgive. Nobody will forget.”

Meanwhile, the Russian military convoy threatening Kyiv and its nearly 3 million residents was far bigger than initially thought, with satellite images showing it occupying much of a 40-mile (64-kilometer) stretch of road north of the capital. The convoy was no more than 17 miles (25 kilometers) from the city center on Monday, according to satellite imagery from the Maxar company.

Zelenskyy called on NATO to enforce a no-fly zone over Ukraine for Russian airplanes, helicopters and missiles, but Britain’s deputy prime minister rejected the idea, saying it would risk widening the war by putting the alliance in direct conflict with Russian forces.

Kyiv’s outgunned but determined troops have slowed Russia’s advance and held onto the capital and other key cities. But the attacks have taken a toll.

Brovary, east of Kyiv across the Dnieper River, sustained heavy damage, including charred vehicles, flattened military trucks and at least one bombed-out building. A hospital received at least three dead members of Ukrainian security forces at its mortuary. Valentin Bagnyuk, chief doctor at the Brovary Central District Hospital, said Tuesday there was an explosion that injured at least six people.

And Russian strikes on the key port city of Mariupol seriously wounded several people Tuesday. Separatist forces in Donetsk said they established two corridors for the evacuation of civilians from Mariupol, which suggests that a large attack on the city could be imminent.

Russian forces have blocked the major Black Sea port city of Kherson, according to Ukrainian officials. And Russian artillery hit a military base in Okhtyrka over the weekend, killing more than 70 Ukrainian soldiers, the head of the region wrote on Telegram.

U.N. humanitarian coordinator Martin Griffiths said Tuesday that shelling and bombing have damaged pipes, electricity lines and basic services in Ukraine, and that hundreds of thousands of families are without drinking water.

WAR SANCTIONS AND WORKAROUNDS

Western officials believe Russian President Vladimir Putin wants to overthrow Ukraine’s government and replace it with a compliant regime, reviving Moscow’s Cold War-era influence.

The United States and European Union have levied sanctions on Russia’s biggest banks and its elite, frozen the assets of the country’s Central Bank located outside the country, and excluded its financial institutions from the SWIFT bank messaging system — but have largely allowed its oil and natural gas to continue to flow freely to the rest of the world.

Sanctions experts expect Russia to try to mitigate the impact of the financial penalties by relying on energy sales and leaning on the country’s reserves in gold and Chinese currency. Putin also is expected to move funds through smaller banks and accounts of elite families not covered by the sanctions, deal in cryptocurrency and rely on Russia’s relationship with China.

WHAT HAPPENED AT THE UNITED NATIONS?

The U.N.’s two major bodies — the 193-nation General Assembly and the more powerful 15-member Security Council — held separate meetings Monday to discuss Russia’s war on Ukraine.

The council meeting opened with the news that the United States was kicking out 12 Russian U.N. diplomats whom Washington accuses of spying.

The assembly will give all U.N. members an opportunity to speak about the war and more than 110 signed up to do so, with speeches continuing Tuesday. The assembly, which allows no vetoes, is expected to vote later in the week on a resolution coordinated by European Union envoys, working with Ukraine.

The draft resolution, obtained by The Associated Press, demands that Russia immediately stop using force against Ukraine and withdraw all troops.

In Geneva, meanwhile, scores of diplomats walked out of two meetings at the U.N. in which Russian Foreign Minister Sergey Lavrov was beamed in for a video statement, as a protest against Russia’s invasion of Ukraine.

The International Criminal Court’s chief prosecutor said he plans to open an investigation “as rapidly as possible” into possible war crimes and crimes against humanity in Ukraine — both alleged crimes committed before the Russian invasion, but also any new crimes that either side might have committed since the invasion started.

HOW MANY PEOPLE HAVE FLED UKRAINE?

The U.N. refugee agency says that about 660,000 people have fled Ukraine for neighboring countries since the Russian invasion began. The number, given on Tuesday, was up from a count of more than 500,000 a day earlier.

UNHCR spokeswoman Shabia Mantoo said in Geneva that “at this rate, the situation looks set to become Europe’s largest refugee crisis this century.”

Earlier, when the overall figure still stood at around half a million, she said the count included 281,000 in Poland, more than 84,500 in Hungary, about 36,400 in Moldova, over 32,500 in Romania and about 30,000 in Slovakia. The rest were scattered in other countries, she said.

U.N. High Commissioner for Refugees Filippo Grandi, has said the U.N. expects the total to reach 4 million in the coming weeks.

WHAT’S HAPPENING TO THE RUSSIAN ECONOMY?

Sanctions are “going to cause the Russian economy to collapse,” French Finance Minister Bruno Le Maire told France Info radio on Tuesday. Nations have blocked some Russian banks from the SWIFT international payment system and are restricting Russia’s use of its massive foreign currency reserves.

Russia’s central bank took drastic steps to prop up the plunging ruble on Monday, but foreign investment is flooding out of the country.

Oil companies such as BP and Shell have pulled out of their stakes in Russian energy ventures. Norwegian Oil and Gas, an association for oil and supplier companies in the world’s third-largest natural gas exporter, followed suit Tuesday by suspending two Russian companies.

The French energy conglomerate TotalEnergies said it wouldn’t fund any new projects in Russia, but it stopped short of abandoning its holdings there.

The company that runs the Nord Stream 2 natural gas pipeline, which was built to bring Russian gas to Europe but was suspended by Germany after the invasion, is laying off all employees at its Swiss headquarters. Switzerland’s economy minister, Guy Parmelin, told Swiss broadcaster RTS that more than 140 people were affected.

Non-energy companies have also been affected, with the world’s biggest shipping company, A.P. Moller-Maersk, announcing that all new bookings to and from Russia “will be temporarily suspended, with exception of foodstuffs, medical and humanitarian supplies.”

(AP)