Fernando Lugo has denounced his removal from Paraguay's presidency as a "parliamentary coup" and said he would join those urging a "peaceful strike".
In his first public comments since his impeachment and removal from office on Friday, Mr Lugo condemned the "coup against the citizenry and democracy".
He was making a surprise early morning appearance at a TV channel in Asuncion.
Mr Lugo was impeached over his handling of deadly land clashes, sparking condemnation from regional neighbours.
The 39-4 impeachment vote in the Senate followed clashes between farmers and police last week that left at least 17 people dead.
'Return of dictatorship'
Mr Lugo appeared for an early morning television programme hosted by a state-funded public television channel.
The "open microphone" programme had drawn a long line of people angry at the impeachment.
"We will not recognise any other president," the crowd of 200 people chanted.
Mr Lugo referred to the withdrawal of ambassadors by Brazil, Argentina and Uruguay, accusing the new Paraguayan government under Federico Franco of "isolating the country".
"They will be responsible for the poverty and the return of dictatorship in Paraguay," Mr Lugo said.
He added: "Our nation calls us for a peaceful strike, and as a Paraguayan citizen, today I join this strike."
Mr Lugo said: "Without doubt it is a coup, a parliamentary coup, a coup against the citizenry and democracy, and we have to shout that to the four winds."
Mr Franco, who had been sworn in immediately after the impeachment, denied there was any coup.
"The country is calm. I was elected (vice president) in 2008 by popular vote. Activity is normal and there is no protest," he said.
Mr Franco appointed Jose Felix Fernandez as foreign minister, saying he would send him to "Argentina, Brazil and Uruguay to meet with authorities and explain to them that there was no break with democracy here".
The impeachment brought protests from around the region. Cuba called it a "parliamentary coup d'etat", Chile said it "did not comply with the minimum standards of due process", while Colombia said it was an abuse of legal procedures.
The US urged "all Paraguayans to act peacefully, with calm and responsibility".