A Somali policeman and a U.N. official say that gunmen have attacked the U.N. compound in Mogadishu with a bomb guns.

Police officer Abdi Hassan described the gunfire as "heavy"

A U.N. official said the attack Wednesday is against a building just outside the secure airport compound where all the U.N. agencies are based. The official said she was close to the U.N. compound when the blast occurred but is not inside. She said that U.N. security officers are battling the gunmen.

The U.N. official, who said she could not be quoted by name because she is not the official spokeswoman, said the gunmen had not yet been able to get inside the U.N. compound.