A special team of about 50 U.S. Marines has arrived in Haiti to bolster security at the American Embassy as unrest escalates in the Caribbean country.

The Marines are from a so-called FAST team, a Fleet Anti-Terrorist Security Team. The U.S. Ambassador in Haiti requested dispatch of the special force to protect the Embassy and American personnel after a small military group visited Port-au-Prince last week to assess security.

Defense officials have called the moves "prudent" but decline to say whether an evacuation operation is under serious consideration.

The deployment of the FAST team follows the takeover by armed rebels of Haiti's second-largest city, Cap-Haitien, and a threat by the insurgents to march on the capital to oust President Jean-Bertrand Aristide.