A spokesperson for Zimbabwe's largest trade union said police have arrested the secretary general of the Zimbabwe Congress of Trade Unions, Japhet Moyo.
He was arrested at the airport in Harare on Monday and lawyers are checking with police to see why. His organisation had called for last week's nationwide strike to protest the government's action to more than double the price of fuel.
The strike and protests sparked off a government crackdown in which 12 people were killed, according to human rights groups.
More than 600 people, including opposition members of parliament, have been arrested in connection with last week's protests. The labor federation called for last week's job stay away.