A four-day general strike over rising fuel prices has begun in Nigeria, Africa's largest oil producer.
The largest trade union grouping in the country, the Nigerian Labour Congress, said more strikes would follow if a 25% price increase was not reversed. Domestic fuel subsidies were partly removed last year, prompting the rise.
Adams Oshiomhole, the NLC president (a 29-union umbrella body) has led two widely observed general strikes in the last 18 months over fuel price increases.
Nigeria is the largest producer of crude oil in Africa, but two-thirds of the population live in poverty. The bulk of the population lives on less than $1 a day and many people feel the only benefit they ever see from the country's oil is cheap, subsidised fuel.
The union leader was detained on Saturday in the country's capital, Abuja. Mr Oshiomhole said he was picked up by state security service operatives on the tarmac of the domestic airport in Abuja, as he was about to board a plane.
He said the 15-men strong security service team wanted him "to follow them to their boss" without producing any warrant. After he refused to go, he said he was treated "very rough" by the officers.
The state security services say Mr Oshiomhole was allowed to go home on Saturday, after answering questions over what they describe as a misunderstanding with field operatives.