United Nations officials said late Tuesday they were having trouble contacting the UN mission in Haiti to get a clear picture of the huge earthquake that struck the Caribbean island nation.

"We are trying to get in touch with our people on the ground but we are experiencing communication problems, which is not unusual in a disaster such as this," Stephanie Bunker, spokeswoman for the UN Office for the Coordination of Humanitarian Affairs, told AFP here.

The 7.0 quake toppled buildings and caused widespread damage and panic, according to Haitian officials and AFP witnesses.

Bunker said OCHA sent alerts to its other offices around the world to prepare for a major relief effort.

And UN spokesman Martin Nesirky also said communication problems made it difficult to piece together information on the scale of the disaster.

Attempts to reach Alexandra Duguay, a spokeswoman for the UN mission in Haiti (MINUSTAH) in Port-au-Prince, by telephone, through e-mail, Facebook or Twitter proved unsuccessful.