LUANDA (REUTERS) - Angola on Friday denied a report by Portuguese state TV that the oil-producing African state's long-serving President Jose Eduardo dos Santos was undergoing cancer treatment in Spain.

"I don't have anything to say, because it is not true," Angolan Foreign Minister Georges Chikoti told reporters in Luanda.

The RTP report, broadcast late on Thursday, said Mr dos Santos had checked in to the oncology unit of a clinic in Barcelona. A follow-up report on its website said he was about to undergo surgery.

Neither report cited any sources.

The 71-year-old dos Santos has been in power in Africa's second-biggest oil producer since 1979, making him the continent's second longest-serving leader.

He was elected for a new five-year term in August 2012, but has long kept observers guessing about his political plans and who might succeed him.

Mr dos Santos travelled to Barcelona from Luanda on Nov 9 on a private visit. Earlier this year, he spent 56 days on a private visit abroad, and the Angolan news agency ANGOP said then he was in Spain, although it was no clear if he spent all of his trip there.