CARACAS: Venezuelan President Hugo Chavez will appear on Monday at his biggest rally since he was diagnosed with cancer a year ago, providing clues to the state of his health as he heads into a re-election campaign.

The former soldier is expected to make a dramatic re-entry onto the political stage at the rally to effectively launch his campaign following a long absence due to cancer treatment and months of mystery and rumor about the extent of his illness.

Throngs of Chavez's red-shirted fans gathered in downtown Caracas as the 57-year-old leader prepared to register himself as a candidate for the Oct 7 presidential election. Several giant inflatable Chavez dolls waved its arms above the crowd.

A return to his thundering speeches before pulsing crowds is all the more important after his opposition rival, Henrique Capriles, put on a show of youthful vigor on Sunday by leading a 10 km (6.2 mile) march with hundreds of thousands of supporters to register his candidacy.

Chavez's appearance on Monday will dispel rumors he might have had to sign up for the election online due to his illness.

“The opposition believe the fable that the president was not going to register, that he would not go in person,” said Foreign Minister Nicolas Maduro, a close ally who Venezuelan analysts have suggested could be a potential successor.

“This is the hour of the fatherland. We are going to register Hugo Chavez for the great victory we will achieve.”

A turn for the worse in Chavez's health could mean the end for his movement - a blow to global leftist leaders who see him as an inspiration, but a boon to investors seeking free market reforms in Venezuela and oil companies keen on tapping the world's biggest crude reserves.

His allies have kept his image in the public eye for months with rallies in which he was notably absent or appeared only via Twitter messages that cabinet ministers read out live.

Chavez has at times seemed to revel in the rumors of his imminent demise, which range from him being confined to a wheelchair to reports that he has only two months to live.

All eyes on Chavez

Last year he said he underwent two operations to remove a baseball-sized tumor, and this year had a third operation only months after having declared himself “cancer free.” His true condition is a guarded state secret.

“All eyes will be on Chavez to see how healthy he is and his ability to move and walk,” Russ Dallen, head trader of Caracas-based BBO Financial Services, wrote in a research note.

Most of the country's main pollsters show Chavez holding a double-digit lead over Capriles. But Venezuela's public opinion is known to shift dramatically, as it did when Chavez came from behind in 1998 to win his first election.

On Saturday, Chavez spoke extensively with reporters, joking and telling stories while standing on the steps of the presidential palace in a live television appearance.

He said a battery of medical exams had come out “absolutely fine,” but did not say whether he would need more treatment.

Supporters sent Twitter messages with the hash tag #VoyconChavez (#I'mgoingwithChavez). Adversaries responded by filling Venezuela's notoriously vitriolic Twitter-sphere with messages tagged to #13aosdementiras (#13yearsoflies).

Critics accuse Chavez allies of using state resources to swell demonstrations and forcing government employees to attend.

Opposition leader Leopoldo Lopez said the ruling Socialist Party had ordered ministries to help bring 120,000 people to the march, citing what he called an internal party document.