Chief UN war crimes prosecutor Carla Del Ponte says she has delivered to Belgrade two indictments linked to the Srebrenica massacre during the Bosnian War in 1995.

After meeting Yugoslav Foreign Minister Goran Svilanovic in Belgrade, Mrs Del Ponte told reporters she had brought two sealed documents with her from The Hague, which had now been unsealed.

It is a fact that we have so many fugitives who are under arrest warrant and who are not arrested

Carla Del Ponte

But she refused to reveal the names of those charged or any other details, saying the indictments would be made public later in the day.

More than 8,000 Bosnian Muslim men and boys were killed when the town of Srebrenica, officially placed under the protection of UN peacekeepers from the Netherlands, fell to Bosnian Serb forces in July 1995.

Improving co-operation

Mrs Del Ponte is in Belgrade for talks with Mr Svilanovic and Serbia's Prime Minister Zoran Djindjic.

The talks are aimed at speeding up co-operation between Belgrade and the UN tribunal, notably on the extradition of war crimes suspects believed to be in hiding in Yugoslavia.

Ratko Mladic is believed to be hiding in Serbia

A statement issued after the talks said Mrs Del Ponte "expressed dissatisfaction" over Belgrade's lack of co-operation.

"It is a fact that we have so many fugitives who are under arrest warrant and who are not arrested," she said.

In the past Mrs Del Ponte has particularly complained that former Bosnian Serb commander Ratko Mladic - whom she insists is hiding in Serbia - still remains at large.

Search for Mladic

During her last visit to Belgrade in July, Mrs Del Ponte urged Yugoslav officials to step up the hunt for Mr Mladic.

But the Yugoslav authorities say they do not know where he is.

"No-one at the Justice Ministry has any proof that this person (Mladic) is here," Nebojsa Sarkic, an adviser at the ministry, said on Monday.

"If Del Ponte has such information, she should hand it over," she told independent Belgrade radio station B92. "She has not yet done so."

Slobodan Milosevic is on trial in The Hague

Mr Mladic has been indicted by the UN tribunal for allegedly ordering and carrying out the siege of Sarajevo during the 1992-1995 Bosnian war, as well as the massacre in Srebrenica.

Along with Mr Mladic, Bosnian Serb leader Radovan Karadzic also tops the list of the UN tribunal's most wanted suspects.

Mr Karadzic is believed to be living in hiding in the Serb-controlled half of Bosnia.

Yugoslavia has been under constant pressure from the international community to hand over all war crimes suspects, since last June's extradition of former president Slobodan Milosevic.

Mr Milosevic is currently on trial for war crimes in Bosnia, Croatia and Kosovo during the 1990s.

Belgrade has so far failed to apprehend any of the suspects still at large, despite passing legislation earlier this year to allow the extradition of Yugoslav citizens to the court.

Six Serbs voluntarily surrendered in the spring.