"Today brave soldiers, brave patriots, brave men supporting the Constitution have answered our call," Guaido said in the video recorded with a small group of uniformed men.

At the same time opposition politician Leopoldo Lopez said he had been "freed" from jail 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.

The Venezuelan government of President Nicolas Maduro quickly denounced an "attempted military coup."

"At this moment we are facing and deactivating a small group of treacherous military personnel" that gathered "to promote a military coup," communications minister Jorge Rodriguez tweeted, referring to the case as an "attempt" by right-wing operatives.

Government officials then called for supporters to rally at the presidential palace in Caracas.

In Madrid, the government warned against a "bloodbath."