Venezuelan President Hugo Chavez has suffered more complications following complex cancer surgery in Cuba and remains in a "delicate" condition.

Vice President Nicolas Maduro gave the update in a televised statement broadcast from Havana.

Mr Maduro flew to Cuba to visit Mr Chavez in hospital as supporters' fears grew for the ailing 58-year-old socialist leader.

The President has not been seen in public nor heard from in three weeks.

He had already suffered unexpected bleeding caused by a six-hour operation on 11 December for an undisclosed form of cancer.

Officials said doctors then had to fight a respiratory infection.

In a sombre broadcast, Mr Maduro said: "Just a few minutes ago we were with President Chavez. He greeted us and he himself talked about these complications."

"Thanks to his physical and spiritual strength, Comandante Chavez is confronting this difficult situation."

The Vice President, flanked by his wife Attorney-General Cilia Flores, Mr Chavez's daughter Rosa Virginia and her husband, Science Minister Jorge Arreaza, said he would remain in Havana while the President’s condition evolved.

Mr Maduro has previously warned Venezuelans to prepare for difficult times and urged them to keep the President in their prayers.

A senior government official in Caracas said the New Year's Eve party in the capital's central Plaza Bolivar had been cancelled.

Mr Chavez's resignation for health reasons, or his death, would upend politics in the OPEC nation, where his personalised brand of oil-financed socialism has made him a hero to the poor but a pariah to critics who call him a dictator.

His condition is being closely watched around Latin America, especially in other nations run by leftist governments, from Cuba to Bolivia, which depend on subsidised fuel shipments and other aid from Venezuela for their fragile economies.

Mr Chavez has not provided details of the cancer that was first diagnosed in June 2011.

His allies have openly discussed the possibility that he may not be able to return to Venezuela to be inaugurated for his third six-year term as President on the constitutionally mandated date of 10 January.

Senior officials have said the people's wishes were made clear when the President was re-elected in October.

Opposition leaders say any postponement would be just the latest sign that Mr Chavez is not in a fit state to govern and that new elections should be called to choose his replacement.