UNITED NATIONS (Reuters) - The U.N. Security Council authorized on Tuesday an African Union force in Somalia for another six months, a day after Somalia's government signed a peace agreement with some opposition figures.

A unanimous resolution also asked U.N. Secretary-General Ban Ki-moon to work with the AU to strengthen U.N. logistical, political and technical support to help bring the African Union Mission in Somalia, or AMISOM, up to U.N. standards.

Somalia has been mired in anarchy since warlords overthrew a dictator in 1991. The waters off the Horn of Africa country are considered among the most dangerous in the world for shipping because of rife piracy.

The peace agreement, which was initiated on June 9 in Djibouti and signed on Monday, has been rejected by hard-liners and done little to quell violence.

More than 8,000 civilians have been killed and 1 million uprooted in fighting since early last year pitting President Abdullahi Yusuf's interim administration and allied Ethiopian forces against Islamist rebels.

Last month the AU said it was incapable of stabilizing the situation in Somalia and urged the United Nations to take over peacekeeping operations. The world body has been cautious of stepping in before some kind of peace is established.

AMISOM has authorized the deployment of 8,000 troops but has only 2,600 on the ground.

Nigeria said last week it would deploy a battalion of 850 officers and soldiers to Somalia in the next few weeks to join existing AMISOM forces. AMISOM is made up of soldiers from Uganda and Burundi.

AMISOM was meant to replace Ethiopian troops whose presence inflamed the insurgency because they helped Somalia's government dislodge an Islamist movement at the start of 2007.

A shortage of funds and the violence raging in the capital Mogadishu have prompted several nations to reconsider their offers of troops.

The Security Council's resolution stated a willingness to consider at an appropriate time "a peacekeeping operation to take over from AMISOM, subject to progress in the political process and improvement in the security situation on the ground."