U.S. helicopters carrying more than 100 troops landed at the earthquake-damaged Haitian presidential palace on Tuesday, reports said.

They will help maintain security and reinforce disaster relief there.

Meanwhile, U.S. marines landed southwest of the most-hit Haitian capital of Port-au-Prince to link up with UN peacekeepers.

Days after a deadly 7.3-magnitude earthquake struck Haiti, the capital city was still in an absolute shambles, with hospitals being overcrowded, streets strewn with rubble and panic-stricken people desperate for aid.

Up to now, more than 50,000 people are believed to have died in the strongest earthquake in more than 200 years, according to the Haitian Civil Protection Ministry. The death toll could double.