Nurses and midwives in the Nigerian capital, Abuja, have gone on strike against new rules for verifying their qualifications to foreign nursing boards.
The regulations are meant to curb the exodus of health workers from Nigeria.
Nurses will now be charged verification fees and will have to have practised in Nigeria for at least two years before the authorities will confirm their credentials.
All applications will now take a minimum of six months.
The nurses have said the government should improve their working conditions instead of curtailing their freedom to practise where they want.
The Nigerian authorities said last year that more than 75,000 nurses and midwives had left the country in five years, leading to a huge shortage at home.