Six “terrorists and hired killers” have been arrested in Venezuela, after being accused of trying to assassinate President Nicolás Maduro in an alleged drone attack, the government said on Sunday.

Interior and Justice Minister Nestor Reverol announced the arrests on state television, saying that more could be on the way “in the coming hours”.

Three soldiers were in critical condition and four more were injured in the alleged attack that involved two remote-controlled drones, Mr. Reverol said. He described it as “a crime of terrorism and assassination” and said that the “material and intellectual authors inside and outside the country” had been identified.

Mr. Maduro had pointed the finger at outgoing Colombian President Juan Manuel Santos and “the ultra-right wing” — a term he uses to describe domestic opposition — even as a mysterious rebel group claimed responsibility.

Nicmer Evans, a former government loyalist and now leader of the Opposition Frente Amplio party, said he feared the government’s measures “open the door to persecution and a wave of repression.”

Army general Padrino Lopez described Saturday’s incident as “an aggression against the military” aimed at provoking regime change “through unconstitutional means”.

The alleged attack involved two drones, each carrying a kg of the plastic explosive C4, which Mr. Reverol said on state television is “capable of causing effective damage over a 50-metre radius.”

State television images showed Mr. Maduro looking up with a start after hearing a bang, as National Guardsmen lined up in the parade scattered in fright.

No drones could be seen in the television broadcast.

On Saturday, a policeman told AFP that drones may have been released from a nearby apartment that suffered a fire after one exploded. However, other accounts blamed the fire on the accidental explosion of a gas cylinder.

Mr. Maduro’s allies Cuba, Bolivia, Syria and Iran condemned the incident, as did Russia. Spain rejected “any type of violence for political ends”.