News of the president's medical leave sparked a flurry of talk in Nigeria that Buhari, 74, was unwell, and potentially very sick. Those claims have been fueled by a previous illness, when he spent nearly two weeks in London last June treating an ear infection.

Minister of Information and Culture Alhaji Lai Mohamed said the government urged Nigerians "to disregard the subversive messages being circulated via text messaging and the Social Media, saying the fabricated messages are being orchestrated by those who feel threatened by the emerging order."

"There is no iota of truth in the messages being circulated on the health of the President, who is hale and hearty, and the purported emergency meetings of the State Governors in Abuja or anywhere," he said in a statement.

Sources of the allegations about Buhari's wellbeing are being investigated, the minister said.

Buhari's predecessor, Goodluck Jonathan, was sworn in after the death in 2010 of President Umaru Yar'Adua. His illness created a power vacuum that was only filled by Jonathan, his vice president, after three months of political infighting.

Buhari is expected to resume work on Feb. 6, his spokesman said when the president departed last week.

When Buhari had been in London for medical treatment last June, the People's Democratic Party, Nigeria's main opposition, had said that he was "critically ill" and he had returned to Abuja to continue treatment, without giving a source for the information.