In a speech broadcast on national TV Saturday evening, the socialist Maduro also blamed the "Venezuelan ultra-right in alliance with the Colombian ultra-right" and charged that President Juan Manuel Santos was "behind the attack."

"I must inform you that some of the actors (responsible for the attempt) on my life have been captured and are being charged," Maduro told the TV audience. "Some of the evidence has been taken, and I won't say more except that the investigation is much advanced."

The attack unfolded as Maduro, wearing a presidential sash, addressed an afternoon ceremony marking the 81st anniversary of the Venezuelan national guard. The event was held on a downtown Caracas thoroughfare decorated in the national colors of yellow, red and blue, and hundreds of troops stood in formation as Maduro spoke, flanked by officials and military officers.

Video of the event showed Maduro and his wife, Cilia Flores, and others on the podium looking curiously skyward. Then all flinch at some sound. The camera cut away to an overhead shot that showed soldiers breaking ranks and scattering to take cover.

In his televised address, Maduro said he thought at first that the explosions were fireworks. "Then a microsecond later there was a second explosion behind the stage and you saw people running," he said. He was immediately whisked away from the stage.

"At 5:41 p.m. explosions were heard that corresponded to drones carrying explosive charges that went off near the presidential stage," said Communications and Information minister Jorge Rodriguez in a statement broadcast on state TV.

Rodriguez also described the bombs, which exploded at the end of the ceremony, as an attempt on Maduro's life. It was unclear how many bombs were deployed.

 A spokeswoman for Santos said Saturday night that Colombian armed forces have not been put on special alert in the aftermath of Maduro's charges.

Santos, whose second term ends Aug. 7, has said in recent interviews that he believes Maduro's government is in its "final days."

Although Maduro's predecessor, Hugo Chavez, was helpful in bringing the Revolutionary Armed Forces of Colombia to peace negotiations that culminated in a 2016 peace accord, relations between Santos and Maduro have deteriorated partly because of an influx of Venezuelan refugees into Colombia in the last two years.

Before the attack, Maduro denounced a "permanent conspiracy" to sabotage the nation's electrical system, a reference to the frequent power outages hitting Venezuelan cities over the last several days. Critics say the outages are a result of insufficient investment and government neglect.

"The people should know that there is an electricity war but count on the national guard to pursue and capture those responsible," Maduro said in his speech during the military ceremony.