Venezuela's all-powerful constituent assembly is launching proceedings Wednesday to try opposition lawmakers over a failed "attack" on President Nicolas Maduro, who also accused exiled opposition leader Julio Borges.

Constituent Assembly chief Diosdado Cabello called the session to strip the lawmakers of their parliamentary immunity so they could face trial for the alleged and failed bid to kill the president.

"When justice comes, it hits hard," Cabello said.

Maduro and his government said the president had been targeted by two flying drones each carrying a kilogram (2.2 pounds) of powerful C-4 explosives. 

But details of Saturday's incident remain unclear, with conflicting information coming from various sources.

The Maduro administration said Colombia -- including ex-president Juan Manuel Santos, who ended his term Tuesday -- had collaborated on the attack with the "ultra far-right" Venezuelan opposition, and it was financed by unnamed figures in the US state of Florida.

No evidence was given to support the allegations, which have worsened already fraught ties between Caracas and Bogota.

In a television and radio address, Maduro simultaneously accused opposition legislator Juan Requesens and Borges of having plotted a drone "assassination" attempt on the Socialist leader over the weekend.

The president said several raids were underway as part of investigations.

Borges is one of the most prominent figures of the Venezuelan opposition and like Requesens a member of the Primero Justicia (Justice First) party of former presidential candidate Henrique Capriles.

Primero Justicia said Requesens and his sister Rafaela were "arrested and hit" in a sweep by the SEBIN national intelligence service unit. Rafaela was later released.

"All the statements (of detained suspects) point to Julio Borges, who lives in a mansion in Bogota protected by the outgoing government of Colombia, we know he has the cowardice to participate in this type of events," Maduro said. 

He also railed against Requesens, describing him as one of his "craziest and most psychopathic" adversaries.