Islamic courts that control much of southern Somalia are claiming authority over the entire country.

A top official, Sheikh Sharif Ahmed, declared the courts' authority while talking to reporters in the capital, Mogadishu Thursday.

He said the courts' executive body will now be known as the Supreme Islamic Council of Somalia. Ahmed also confirmed that a radical cleric, Sheikh Hassan Dahir Aweys, has replaced him as the courts' overall leader.

Quick objections to the announcement came from officials of Somalia's U.N.-backed transitional government. The French News Agency, AFP, quotes the information minister, Mohamed Abdi Hayir as saying the Islamic courts are not a national institution.

The courts and the government signed a cease-fire and mutual-recognition agreement last week in Sudan.

However, the government has little power outside its base in the city of Baidoa. Fighters loyal to the Islamic courts recently seized control of Mogadishu and other Somali cities.

This week, Islamic fighters have been trying to dismantle the remaining checkpoints around Mogadishu held by secular warlords. At least five people were killed in a clash south of the capital on Tuesday.

Many Somalis have applauded the Islamists for asserting control over Mogadishu. The capital and the country have been without an effective central government since 1991.

However, the United States has expressed concern that Somalia may turn into a haven for terrorists. Other critics say they fear the Islamic courts will attempt to impose a Taleban-style regime over Somalia.

The United States has said it will have no dealings with Sheikh Aweys, the Islamic courts' new leader. He is on U.S. and United Nations lists of terrorist suspects.

Some information for this report was provided by AFP and Reuters.