"The Bosnian Serbs removed one tank from the Bare weapons collection point at 2115 hours (on Tuesday) and they had already taken a 100mm gun from Hreza at lunchtime," Myriam Souchaki, a U.N. spokeswoman in Sarajevo, said on Wednesday.

Bare and Heza are two of nine U.N. weapons depots around Sarajevo which Bosnian Serbs have blockaded and taken virtual control of in the past 12 days.

Tanks and big guns have been fired into the city from some of the depots and a number of weapons have been hauled away for use elsewhere.

The U.N. Security Council created a heavy weapons exclusion zone around Sarajevo in February of 1994, backed by the threat of NATO air power.

Most big guns were withdrawn from range of the city or surrendered to U.N. weapons depotsat the time.

But the Serbs, emboldened by lax U.N. enforcement, have gradually disregarded the Sarajevo weapons exclusion zone to the point where they were routinely invading U.N. depots and firing from them.

A day of heavy Bosnian Serb attacks around Sarajevo on May 24 led to a U.N. ultimatum which was ignored, triggering two NATO air strikes against Serb ammunition dumps east of the city.

The Serbs responded by shelling five U.N. `safe areas' and blockading or taking hostage nearly 400 U.N. personnel on their territory, including a number guarding weapons collection sites around Sarajevo.

Bosnian Serbs have since released some of the U.N. peacekeepers and military observers, but 148 still remain surrounded or detained by the Serbs.

U.N. officials in Sarajevo say they are waiting for guidance from United Nations headquarters in New York on whether to try to re-establish the Sarajevo exclusion zone and enforce Bosnian `safe areas' or scale back the peacekeeping mission.