Venezuelan opposition leader and self-proclaimed acting president Juan Guaido said on Tuesday that troops had joined his campaign to oust President Nicolas Maduro as the government vowed to put down what it said was an attempted coup.

“We are currently facing and deactivating a small group of treacherous military personnel who took positions in the Altamira distributor road (in Caracas) to promote a coup d’etat,” Communications Minister Jorge Rodriguez said on Twitter.

“We call on the people to remain on maximum alert to with our glorious National Bolivarian Armed Forces defeat the attempted coup and preserve peace,” he said.

In a video recorded at a Caracas military air base posted on social media, the US-backed Guaido said troops had heeded months of urging to join his campaign to oust Maduro.

“Today brave soldiers, brave patriots, brave men supporting the constitution have answered our call,” he said.

He appeared alongside high-profile opposition politician Leopoldo Lopez who had been put under home arrest by Maduro’s regime but who announced he had been “freed” by soldiers supporting Guaido.

Lopez posted a picture on Twitter with men in uniform, and said it was taken at the Carlota military base.

“Venezuela: the definitive phase to end the usurpation, Operation Liberty, has begun,” read the message.

Venezuela’s Defence Minister Vladimir Padrino Lopez asserted on Twitter that the situation in military barracks and bases in the country was “normal”.

Tensions in Venezuela have been ratcheted up to a critical level this year, after Guaido, who is head of the opposition-ruled congress, announced January 23 that he was the acting president under the constitution.

He said Maduro had been fraudulently re-elected in 2018.