Nigeria's state security service arrested the president of its largest labour federation on Monday on charges that are yet to be disclosed, the Nigeria Labour Congress (NLC) said.

The arrest of Joe Ajero comes days after he criticised the government for raising the price of gasoline by 39%, threatening to call a strike if the decision was not reversed. High fuel prices were among the reasons for cost of living protests in early August.

Ajero was arrested by officials from the Department of State Security (DSS) at the airport in the capital Abuja while trying to fly to Britain on union business, the NLC said on X.

The DSS did not immediately comment on the issue.

Analysts say the latest hike in the price of gasoline - widely used by small businesses and households to power generators - could further stoke inflation that is already in double digits, worsening economic hardship.