A day after pro-Russia separatists shot down a Ukrainian plane, killing 49, a bomb was found near the office of new Ukrainian President Petro Poroshenko, a security source told Reuters on Saturday. The bomb was defused.

"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," the security source said. “It was a really powerful device.”

The discovery of the bomb came a day after rebels shot down a Ukrainian military plane in Luhansk, which was carrying 49 passengers and military equipment.

Poroshenko, a billionaire businessman, was sworn in as president last week after winning Ukraine’s presidential election late last month. He succeeded Viktor Yanukovich, who fled the country earlier this year amid protests. The Russia-allied Yanukovich fled to Moscow shortly after his ouster.