"In the early morning hours we found a certain amount of explosives at two separate locations inside the memorial centre" in Potocari, just outside Srebrenica, police spokesman Radovan Pejic said on Tuesday.

"We have indications about the people who planted the explosives and we are working on their detention," he added.

The area around the memorial centre was blocked and evacuated. Police units with sniffer dogs were scouring the wider Srebrenica area.

Police initiated the search after receiving a warning from European Union peacekeepers (EUFOR) on Monday evening. EUFOR spokeswoman Brigite Rose said "intelligence sources" had tipped off investigators.

Srebrenica massacre

Some 50,000 people are expected to gather at the memorial centre in Potocari on 11 July to commemorate the 10th anniversary of the Srebrenica massacre, the worst in Europe since the second world war.

Mladic, wanted for the Srebrenica
massacre, is still at large

British Foreign Secretary Jack Straw and EU Enlargement Commissioner Olli Rehn are among the international officials invited to the memorial ceremony.

Bosnian Serb forces and irregular Serbian police units killed some 8000 Muslim men and boys over several days in July 1995 after the UN-protected enclave was overrun.

The alleged masterminds of the massacre - Bosnian Serb wartime leader Radovan Karadzic and his former army chief, Ratko Mladic - have been on the run for a decade since they were charged with genocide by the UN war crimes tribunal at The Hague.