Morgan Tsvangirai, a long-time rival of Zimbabwean President Robert Mugabe, was airlifted to a hospital in Johannesburg, South Africa, early Friday morning. He reportedly became ill during a party meeting near Zimbabwe's capital Harare.

Government spokesman Luke Tamborinyoka said Saturday that Tsvangirai is in "a very stable condition," confirming previous reports citing sources within Tsvangirai's Movement for Democratic Change (MDC) party.

The 65-year-old former prime minister is in South Africa "for a routine medical procedure," according to Tomborinyoka. Other sources within the MDC had told the news agency Reuters that the sudden illness was not related to Tsivangirai's treatment for colon cancer that started last year.

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"We are monitoring the situation. He will be fine, it's only that he was overwhelmed with work and his health deteriorated," another anonymous source told news agency AFP.

Tsvangirai had been attending an MDC meeting Thursday evening in Kadoma around 160 km (100 miles) southwest of Harare. While there, he reportedly started suffering from severe vomiting.

The former trade union leader plans to challenge Robert Mugabe in next year's presidential elections. Mugabe, 93, also reportedly suffers from poor health and regularly travels to Singapore for treatment.

Zimbabwe's vice president, Emmerson Mnangagwa, was also flown to South Africa for medical treatment in mid-August after falling ill at a Mugabe rally in the south of Zimbabwe. Some Zimbabwean media outlets had reported that Mnangagwa had been poisoned.

Tsvangirai was prime minister between 2008 and 2013 as part of a power sharing agreement with President Mugabe's party, the Zimbabwe African National Union–Patriotic Front (ZANU-PF). He had won the largest share of the vote during the first round of the 2008 presidential election, but rescinded his nomination before the final voting round after violent attacks against MDC supporters.

ape/cl  (AP, AFP, Reuters)