Somalia Islamic militia members sit on a truck carrying an anti-aircraft gun that they seized from secular alliance of warlords, June 5, 2006 after they took control of Mogadishu's Deyniile neighborhood

The United States has expressed concern that Somalia could become a haven for terrorists, amid claims by Islamic militias that they have taken control of the capital Mogadishu.

The U.S. position was put forward by a State Department spokesman Monday, after the chairman of Mogadishu's Islamic Courts Union Sheikh Sharif Sheikh Ahmed declared victory over an alliance of warlords in a radio broadcast.

The chairman urged residents to accept the new leadership, saying the courts want to restore peace and security to the city.

Most of the warlord alliance leaders are said to have fled Mogadishu.

Somali political leaders have accused the United States of backing the warlords, a charge U.S. officials will not confirm or deny.

The warlord alliance has accused the Islamic court militia of having ties to al-Qaida.

Over the past week Islamic fighters allied to the sharia courts pushed the warlords from several Mogadishu strongholds.

The Islamic courts say they can bring order to Somalia, which has not had an effective central government for more than 15 years.