PHOTO LINK BELOW: The major earthquake which struck southern Haiti on Tuesday, knocked down buildings and power lines and inflicted what its ambassador to the United States called a catastrophe for the Western Hemisphere’s poorest nation.

Several eyewitnesses reported heavy damage and bodies in the streets of the capital, Port-au-Prince, where concrete-block homes line steep hillsides. There was no estimate of the dead and wounded Tuesday evening, but the U.S. State Department has been told to expect “serious loss of life,” department spokesman P.J. Crowley told reporters in Washington.

The magnitude 7.0 quake — the most powerful to hit Haiti in a century — struck shortly before 5 p.m. and was centered about 10 miles (15 kilometers) southwest of Port-au-Prince, the U.S. Geological Survey reported. It could be felt strongly in eastern Cuba, more than 200 miles away, witnesses said.

Witnesses reported damaged buildings throughout the capital, including the president’s residence and century-old homes nearby. President Rene Preval is safe, but there was no estimate of the dead and wounded Tuesday evening.

The headquarters of the U.N. peacekeeping mission in Port-au-Prince collapsed, a U.N. official told CNN.

There was no immediate report of any dead or wounded from the building, but Alain Le Roy, the undersecretary-general for peacekeeping operations said of the 9,000-member, Brazilian led-force, “For the moment, a large number of personnel remain unaccounted for.”

Because of the earthquake’s proximity to the capital, and because the city is densely populated and has poorly constructed housing, “it could cause significant casualties,” said Jian Lin, a senior geologist at the Woods Hole Oceanographic Institution in Massachusetts.

In Washington, President Obama said the U.S. government would “stand ready to assist the people of Haiti.” At the Pentagon, the U.S. military said humanitarian aid was being prepared for shipping, but it was not yet clear where or how it would be sent. A U.S. aviation source said the control tower at the Port-au-Prince international airport collapsed, possibly hindering efforts to fly relief supplies into the country.

Secretary of State Hillary Clinton told reporters that Washington is offering “our full assistance” to Haiti.”

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