Doctors in Nigeria's economic capital Lagos have gone on strike to protest alleged police harassment of health workers during a dusk-to-dawn curfew aimed at curbing the spread of Covid-19.

Health workers including doctors have been exempted from the curfew as providers of essential services, but the Nigerian Medical Association (NMA) has accused police in Lagos of harassing and detaining its members.

"The Lagos State branch of the NMA has resolved that it is presently unsafe for its members to continue to provide healthcare services under the present confused arrangement," the doctors' body said in a statement late on Wednesday.

National police spokesperson Frank Mba issued a statement saying: "All essential workers, including medical personnel, firefighters, ambulance services, journalists, etc., are exempted from the restriction of movement associated with the partial lockdown and national curfew across the federation."

Nigeria has introduced a raft of measures, including a lockdown as well as the curfew, to curb the spread of the coronavirus.