Chavez will be undergoing what he described as 'rigorous examinations' [EPA]

Hugo Chavez, the Venezuelan president, has returned to Cuba to undergo a series of medical tests to evaluate the progress of his cancer treatment.

The president, who finished what he described as his fourth and final round of chemotherapy in Cuba last month, said he will be undergoing what he described as "rigorous examinations".

"I have faith that we'll get through these tests," said Chavez, speaking at Simon Bolivar International Airport before boarding a plane for Cuba on Sunday.

Chavez, 57, underwent surgery on the island in June to remove a tumour from his pelvic region. He has not revealed what type of cancer he is battling, but he has said that tests have shown no signs of a recurrence.

He expects to return to Venezuela with a few days with "good news".

Chavez, a former paratroop commander who was first elected in 1998, has repeatedly vowed to beat cancer, fully regain his health and sail to a victory in next year's presidential election.

He recently announced that doctors predict his hair will soon grow back, and even joked about growing an "afro" before he begins campaigning for next year's October 7 vote.

Grave condition

Many Venezuelans, particularly the president's critics, are skeptical of his assurances that he is recovering.

Some suspect that Chavez has not revealed all the details regarding his illness because he is in grave condition.

"The president must understand the country cannot continue with this uncertainty regarding his illness," said Gustavo Azocar, an opposition politician and radio talk show host who believes Chavez is unfit to continue governing.

"He has attempted to hide the true circumstances of his health."

Azocar argues Chavez should step down.

"The president is not in physical condition to continue as president," he said.

"He should focus on his medical treatment and follow the instructions of his doctors."