Up to 3,500 US army troops have been ordered to leave for Haiti, said US Department of Defense on Thursday.

The troops are from the US Army's 82nd Airborne Division. The first 100 of them is expected to arrive late on Thursday, a Pentagon official told reporters.

Also on Thursday, the army reportedly ordered three amphibious ships to join the USS Carl Vinson aircraft carrier for relief effort in the quake-stricken Haiti.

Tens of thousands people have been feared dead in a 7.0-magnitude earthquake, which shocked Haiti on Tuesday afternoon. The International Federation of the Red Cross estimated that some 3 million people may have been affected by the earthquake.

(Xinhua News Agency January 15, 2010)