Pakistan's opposition says police have arrested scores of activists in an effort to stop them from participating in weekslong sit-ins in the capital, Islamabad.

Jehanghir Tareen, a leader of the party of famed cricketer-turned politician Imran Khan, said a large number of party activists were captured during overnight raids which started Friday and continued Saturday.

Anti-government cleric Tahir-ul-Qadri also accused police of arresting his supporters.

The arrests came weeks after Khan and Qadri arrived with thousands of protesters aiming to force Prime Minister Nawaz Sharif to resign over alleged voting fraud. Since then, the groups have camped outside parliament, creating political turmoil in the nuclear-armed country of 180 million.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

A powerful car bomb exploded in a bazaar in southwestern Pakistan on Saturday, killing at least three people and wounding 24 others, police said.

Senior police officer Abdur Razzak Cheema said the attack took place when a vehicle carrying security forces was passing through a bazar in Quetta, the capital of southwestern Baluchistan province.

The dead included a paramilitary soldier and two civilians, he said.

"Fortunately, many shops in the bazar were yet to open when the bomb exploded, otherwise it could have caused a big tragedy," he said.

No one immediately claimed responsibility and authorities said they were still investigating to determine who was behind the attack.

Baluchistan is Pakistan's largest province and it has been the scene of low-scale insurgency for the past several years.

Separatists in the region often attack security forces and officials to pressure the government into allocating more wealth from resources like gas and oil extracted from the province.