Belgrade, Serbia-Montenegro ? Two key suspects have been arrested in the assassination of Prime Minister Zoran Djindjic, a senior police official said Saturday.

The official, who spoke on condition of anonymity, refused to give details about the suspects beyond saying they were “very important.”

More than 2,700 suspects have been rounded up since Djindjic was killed in a March 12 sniper ambush.

Serbian Justice Minister Vladan Batic said about 1,000 suspects were still in custody, including several state security and police officials. But the top suspects, including at least three assassins, were still believed to be at large.

The Serbian government has blamed the assassination on the underworld Zemun Clan, a network of mobsters, paramilitary and former security service figures linked to remnants of former Slobodan Milosevic’s regime.