Opposition head stable in South Africa hospital - Spokesman

"He is in South Africa on account of a medical cause. He is being attended to," a senior official from Tsvangirai's Movement for Democratic Change (MDC) told AFP, speaking on condition of anonymity.

"We are monitoring the situation. He will be fine, it's only that he was overwhelmed with work and his health deteriorated."

Luke Tamborinyoka, Tsvangirai's spokesman, disputed what he termed "morbid media reports that he is critical and is battling for his life", insisting he had gone to South Africa for a routine medical procedure and "is in a very stable condition."

Tamborinyoka did not mention what was ailing the former prime minister or the hospital treating him.

Tsvangirai, 65, announced last year he had been diagnosed with cancer of the colon and had begun chemotherapy.

News Day independent daily earlier reported Tsvangirai was airlifted to South Africa early Friday morning after he fell ill.

"He was on oxygen and drip and had been vomiting heavily," the paper said.

Tamborinyoka, however, said Tsvangirai had "urged the nation not to panic about his health" and that he would return in time to campaign for next year’s elections.

President Robert Mugabe, 93, Tsvangirai's rival for over a decade, regularly flies to Singapore, reportedly for medical reasons, thought most details about his health are kept under wraps.

Tsvangirai's party has been riven by divisions since he struck a troubled four-year power-sharing deal with Mugabe after violent and disputed elections in 2008.

The former trade union leader has often accused Mugabe and his government of rigging polls.

In 2008 Tsvangirai won 47.9 percent of the vote to Mugabe's 43.2 percent, which led to a run-off.

But Tsvangirai pulled out before the final round of voting after a spate of violence against his supporters.