Nearly 90,000 people have fled Somalia's capital in recent days, a massive surge of displacements following the heaviest fighting to shake the war-battered city in months, the U.N. said Thursday.

The clashes — the worst between Islamic insurgents and Somali and allied Ethiopian troops since April — have emptied entire neighborhoods, sending 88,000 people streaming from Mogadishu over a three-day period starting Oct. 27, the world body said in a statement.

That contrasts with a previous rate of 20,000 to 25,000 people leaving each month, it said.

"I am also very concerned for the safety and well-being of those remaining in Mogadishu, given the overall insecurity and lack of access and freedom of movement in the city," Christian Balslev-Olesen, a top humanitarian coordinator for Somalia, said in a statement.

More than 100 people injured in the fighting have been admitted to hospitals in just two days, in addition to more than 3,400 civilians wounded since January, Balslev-Olesen said.

Mogadishu has been plagued by violence since government troops and their Ethiopian allies drove out the Council of Islamic Courts in December. For six months, the Islamic group had controlled much of southern Somalia, and remnants have vowed to fight on. Thousands of civilians have been killed in the fighting this year.

According to the U.N., some 1.5 million Somalis are now in need of food aid and protection — 50 percent more than at the start of the year — because of inadequate rains, continuing internal displacement and a potential cholera epidemic, the United Nations said.

Some 450,000 Somalis have fled their homes this year, bringing the total number of displaced people to 800,000, the U.N. said Thursday.

Somalia has not had a functioning government since 1991, when rival warlords overthrew dictator Mohamed Siad Barre and then turned on each other.