President Mahmoud Abbas has outlawed the West Bank's largest labor union and arrested its top two officials in what critics say is a sign of increasing heavy-handedness by the Palestinian leader.

An announcement by Abbas' office followed a series of strikes by the union demanding more benefits. It said the strikes were illegal and "harmed the public interest."

Moayad Amer, an official of the 40,000-member union, said Sunday that officials were trying to get their leaders released. "It is our right to have a union," he said.

The arrests have been seen as a sign of a growing intolerance for dissent by Abbas.

Jihad Harb, an analyst, said Abbas has ruled "in an autocratic way" since losing control of the Gaza Strip to the rival Hamas militant group in 2007.