KIEV (REUTERS) - Ukrainian presidential bodyguards have disposed of a powerful explosive device discovered near President Petro Poroshenko's headquarters, a security source said on Saturday.

"The device was found during the night near the gate where presidential cars go in. It was a container with five grenades and a kilogram of metal nuts," said the source, who declined to be identified. "It was a really powerful device."

The source gave no other details. The presidential administration did not immediately issue any statement.

Poroshenko was sworn in last week after wining an election on May 25. His predecessor, Viktor Yanukovich, was ousted in February after protests in Kiev and the government is facing a rebellion by pro-Russian separatists in east Ukraine.