Updated

Witnesses to Tuesday's "catastrophic" earthquake in Haiti say victims have been buried in the rubble of collapsed buildings.

A reporter for Reuters news agency said he saw dozens of dead and injured people in the debris, which blocked streets in the capital Port-au-Prince.

"Everything started shaking, people were screaming, houses started collapsing. ... It's total chaos," Joseph Guyler Delva said. "I saw people under the rubble, and people killed."

Others described seeing "a cloud of dust" above Port-au-Prince and "many, many" buildings collapsed.

Joel Trimble, a missionary in Haiti, said: "It felt like a train was coming down the road. ... I went outside and the vehicle in the driveway was rocking, glass breaking all around the house.

Trimble also described a house that had collapses and efforts to rescue an elderly woman from the rubble.

"Down in the city, many, many, many buildings had collapsed," he said. There's a cloud of dust over Port-au-Prince right now."

A reporter for the AFP agency said a tractor was already at the scene trying to dig out victims.

Many people fled onto the streets of the impoverished country in panic.

A U.S. government official in Haiti reported seeing houses that had tumbled into a ravine.

"Everybody is just totally, totally freaked out and shaken," said Henry Bahn, a visiting official with the US Department of Agriculture.