Fierce battles were underway Tuesday between Afghan forces and the Taliban in southern Helmand province where the insurgents have almost completely captured a strategic district as Britain deployed military advisers to the restive area.

The development came a day after a Taliban suicide bomber killed six U.S. troops near a Kabul base — the deadliest attack on Americans in the country since August.

A British Ministry of Defense statement late Monday said that “a small number of U.K. personnel” have been deployed to Helmand “in an advisory role.” The U.K. has 450 troops in Afghanistan as part of NATO’s training mission.

The Afghans were also sending reinforcements to Helmand on Tuesday, officials said. Afghanistan’s Chief Executive Abdullah Abdullah said the security of Helmand was a “top priority,” according to his deputy spokesman Javid Faisal.

The Taliban have been getting closer to taking full control of the Sangin district for days, with most government buildings now in Taliban hands.

An official in Helmand said that only an Afghan army base in the district remained in government hands, and it was surrounded by Taliban fighters. Speaking on condition of anonymity because he was not authorized to speak to the media about the operation, the official said Afghan commandos and special forces will try to “rescue those soldiers who are stuck in the base.”

Helmand is important to the Taliban. The lush southern province is home to endless poppy fields and the source of much of the world’s opium, which helps fund the insurgency.

Sangin has particular resonance with the British as more than 100 of their 456 fatalities in Afghanistan since the start of the war in 2001 took place in the district.

The Afghan Ministry of Interior confirmed Tuesday that British troops had arrived at Camp Shorabak, formally the U.S. Marines’ Camp Leatherneck and next door to the camp that was occupied by British forces until the international combat mission ended last year.

Afghan forces “need to strengthen their capacity and improve coordination,” Sediq Sediqqi, the ministry’s spokesman told reporters.

He said the main reason for the length of time it took to send reinforcements to the area was because of its remoteness and, during the summer months, the punishing climate.

“Taking on the responsibility for security from NATO and other international troops was a huge challenge for us,” Sediqqi said, speaking of the Afghan troops who now shoulder full responsibility for the country’s security.

The commander of U.S. and NATO forces in Afghanistan, U.S. Army Gen. John F. Campbell said recently that the Afghan forces were still challenged by practical issues such as logistics, and by lagging confidence.

“There are some places in Helmand they do think the Taliban are 10 feet tall, that they are better trained, they got better weapons,” Campbell told The Associated Press in an interview earlier this month. “It is a confidence thing.”

But the Afghan forces, he said, “will continue to get better. The United States army has been around for 240 years, the Afghan army seven or eight years.”

The Taliban claimed responsibility for the Monday suicide attack on U.S. troops that killed six near Afghanistan’s Bagram airport. Two U.S. troops and an Afghan were also wounded when the bomber rammed an explosives-laden motorcycle into a joint NATO-Afghan patrol.

The soldiers were targeted as they moved through a village near Bagram Airfield, the largest U.S. military facility in Afghanistan with about 14,000 personnel, NATO and Afghan officials said.

The U.S. Embassy in Kabul issued a statement of condolences Tuesday to the families of the dead “as they face such heartbreaking news during the holiday season.”

In New York, Police Commissioner William Bratton said Monday that a New York City police detective, Joseph Lemm, was one of the six American killed in the attack.

Lemm was a 15-year-old veteran of the New York Police Department and worked in the Bronx Warrant Squad. Bratton says Lemm served in the U.S. National Guard and, while a member of the police force, he had been deployed twice to Afghanistan and once to Iraq. He leaves behind a wife and three children.

Secretary of Defense Ash Carter in statement called the attack “a painful reminder of the dangers our troops face every day in Afghanistan.”

It was the deadliest attack on foreign troops in four months. On Aug. 22, three American contractors with the Resolute Support base were killed in a suicide attack in Kabul. On Aug. 7 and 8, Kabul was the scene of three insurgent attacks within 24 hours that left at least 35 people dead. One of the attacks, on a U.S. special operations forces base outside Kabul, killed one U.S soldier and eight Afghan civilian contractors.

(AP)