Serbian PM Vows to Shake Up Secret Service

"There will be changes in the secret service; I believed in the skills of people who didn't show that they have these capacities, but I'll take responsibility for this," Vucic told Serbian public broadcaster RTS on Monday evening.

Vucic also said that the security situation was "even more serious than we expected", referring to the discovery of a weapons cache close to his family's home on October 29.

He said that police had made progress in the case but was waiting for a final report and did not offer any more clues about the suspects or their potential motives.

"There are some testimonies from people who have passed through a lie detector," Vucic said, but didn't say whether he was talking about suspects or witnesses.

On October 29, Vucic was "moved to safety" after police found a large quantities of weapons hidden close to his family home in Jajinci, near Belgrade.

On November 2, Vucic said that security officials and state institutions in charge of his safety must not go public with any more information on the weapons caches reportedly found in and around Belgrade.

The order came after police on November 1 said they had found a new arms stash in a car in a garage in New Belgrade containing 400 grammes of explosives, a detonator, two mobile phones for the remote activation of the explosives, a gun and a submachine gun.

The weapons were found near the premier's brother Andrej Vucic's apartment.

Vucic said that a few months beforehand, several people had been arrested, who turned out to have links to a car found near his brother's apartment when the weapons were discovered on November 1.

"That night when the stashes were found, they would also find a car; a few months earlier, people linked to the car were...