PHNOM PENH, Cambodia — Seeking to quash one of the most serious challenges to the nearly 30-year rule of the country’s authoritarian leader, the Cambodian authorities have banned all public gatherings and summoned two opposition leaders for police questioning.

After months of inaction in the face of growing public dissent to his rule, Prime Minister Hun Sen appeared to signal that he was entering a more aggressive posture toward his critics. The crackdown, including the clearing of protesters from a public square on Saturday, came after a clash on Friday between protesting garment workers and the Cambodian police that left at least four demonstrators dead. The workers have been at the forefront of growing protests against Mr. Hun Sen’s government.

Mr. Hun Sen’s party claimed victory in July elections, which the opposition and independent observers say were riddled with irregularities. Since then, the opposition has called for him to step down and has boycotted Parliament.

The two opposition leaders wanted for questioning, Sam Rainsy and Kem Sokha, said Sunday that they were suspending any protest activity. Mr. Sam Rainsy decried what he called a “facade of democracy” in the country.