Croats battled Bosnia's Muslim-led army for the western half of Mostar on Tuesday, defying a truce intended to cool renewed fighting between the former allies.
Croatian forces were trying to push the Muslims across the Neretva River to the east bank. On Monday, the Croats captured the army headquarters in the city, which was burned out and still smoking Tuesday.
Many Croats want to unite southwestern Bosnia with neighboring Croatia, making the Neretva the eastern boundary of a "Greater Croatia." Similarly, Serbs dream of linking areas they control in Bosnia and Croatia with Serbia, the dominant state in what remains of the Yugoslav federation.
Explosions of artillery shells and heavy machine-gun and sniper fire echoed through Mostar all day, riddling a truce agreed to Monday by Bosnia's Muslim president, Alija Izetbegovic, and Bosnian Croat leader Mate Boban.
French Gen. Philippe Morillon, commander of U.N. peacekeepers in Bosnia, was heading to Mostar with the commanders of the Bosnian army and Croatian forces to discuss the fighting, said Dalgeed Bagga, a U.N. spokesman in Zagreb, Croatia.
A spokesman for the Bosnian Croats, Veso Vegar, said Croats had pushed Muslims back to within 100 yards of the river on the west bank. There was heavy shooting in every direction near the river, and the Croats' hold appeared tenuous.
On Sunday, the Spanish U.N. peacekeeping battalion in Mostar was forced to withdraw to surrounding hills because of the fighting.
The United Nations has said Croatian forces attacked Mostar at dawn Sunday and charged that they were practicing "ethnic cleansing" by herding Muslim civilians out of the city.
Boban charged Monday that government troops started the fighting. Vegar said Tuesday that Muslims attacked a Croatian patrol in the city, killing one Croat soldier and wounding seven.
Eleven Croatian soldiers and one civilian were killed and 100 people wounded in Mostar since Sunday, said Dr. Jadranko Barisic, a Croatian military doctor at Mostar's main hospital.
There was no report on Muslim casualties. Michael Boutin of the non-governmental International Rescue Committee said he assumed there were hundreds of wounded.
On Monday, the top U.N. aid official in the region, Jose Maria Mediluce, charged that the Croats have begun "the second wave of ethnic cleansing."
The U.N. Security Council issued a statement late Monday strongly condemning the Croats, saying the offensive was inconsistent with their leaders' signing of the U.N. peace plan for Bosnia.
The plan would divide Bosnia into 10 largely autonomous regions based on ethnic groups.
Leaders of Bosnia's Serbs, who have captured about 70% of Bosnian territory since they rebelled against a Muslim-Croat vote to secede from Yugoslavia 13 months ago, have refused to sign. The Serbs are to vote on it in a referendum this weekend.
At the United Nations on Tuesday, Bosnian Foreign Minister Haris Silajdzic demanded that U.N. personnel leave his country because their presence, he said, prevents stronger military action.
A statement distributed by Bosnia's U.N. mission said the request was made officially to the Security Council.
In eastern Bosnia, Ukrainian U.N. peacekeepers began efforts to demilitarize Zepa, one of six "safe areas" declared by the United Nations last week after Bosnian Serbs rejected the peace plan.
Ron Redmond, a U.N. aid spokesman in Geneva, said a trickle of people who fled to surrounding hills to escape Serb artillery attacks on Zepa last week were beginning to return, but were in "very, very bad condition."