Mr Mwanawasa is expected to run for a second term in office

The president was admitted to hospital in London for a check-up two weeks ago.

Mr Mwanawasa, 57, has been in office since 2001, and has said he intends to contest elections later this year for a second and final term.

The radio report did not make clear how long ago President Mwanawasa had suffered the stroke.

"Chief Government Spokesman Vernon Mwaanga revealed that President Mwanawasa suffered a minor stroke," Zambian National Broadcasting Corporation radio reported.

"Mr Mwaanga however, said the president was making steady progress," ZNBC said.

There has been speculation in Zambia over the cause of Mr Mwanawasa's illness, prompting opposition groups to demand more information.

Mr Mwanawasa cancelled an election campaign trip and flew to London to see doctors after feeling ill on 1 April, officials said.

But a government spokesman said Mr Mwanawasa had gone to London for a routine check-up to ensure his fitness ahead of the election campaign.