Nigeria's President Muhammadu Buhari, currently on medical leave in the UK, is believed to have talked on the phone with the governor of Kano state. If confirmed, it would be the first time the president has spoken publicly since leaving Nigeria on 20 January.

The phone call could quell rumours that the president is severely ill and unable to resume office, as it has been speculated for the past month.

"We are very grateful for all the efforts Nigerians are putting in — praying for my quick and successful recovery. May Almighty Allah reward you abundantly. My sincere regards to all," Buhari told governor Abdullahi Ganduje, according to the Punch newspaper.

The alleged phone call took place during a prayer session for Buhari organised by the Kano government on 22 February.

The Sahara Reporters website posted on Twitter a video of when the phone call came through.

It is believed some people who attended the prayers burst into tears when they heard the voice of their head of state.

Nigerians are becoming increasingly concerned with the president's health and have been calling on Buhari to personally dismiss allegations of ill health.

People fear a power vacuum at a time when the country is marred by economic recession, terrorism, famine, widespread corruption and religious and ethnic tensions.

Buhari's stay in the UK is shrouded in mystery. The fact that top officials – including the president of the senate, Bukola Saraki – have travelled to London to visit the head of state is further fanning suspicions that the leadership is concealing his true condition.

It is not clear when Buhari is due to return to Nigeria. Before leaving Nigeria, he appointed Vice President Yemi Osinbajo as acting president.

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