Serbia's pro-European Prime Minister Aleksandar Vucic was moved to a safe location Saturday after an arsenal of weapons, including a rocket-launcher, was found close to his house near Belgrade, which a minister said was "preparation for assassination".

Authorities were alerted by passers-by who found the cache in chests in a forest near Vucic's family home in Jajinci, south of Belgrade, Interior Minister Nebojsa Stefanovic told reporters.

"There is a rocket launcher, four hand grenades and a large quantity of ammunition for 7.62 mm automatic rifles and 7.9 mm sniper rifles," said Stefanovic.

"What is worrying is that these weapons were discovered only a few dozen metres from a turn into the family home of Prime Minister Vucic," he said, adding that his retinue would have represented "a very easy target".