MULTAN, Pakistan (AP) — An explosive device killed at least three people on Sunday in the capital of southwestern Pakistan's restive Baluchistan province, despite heightened security as opposition political parties held a large open-air rally in another part of the city, local police said.

The top leaders of an alliance of Pakistan’s major opposition parties have held rallies in two other cities this month as part of a campaign to oust the government of Prime Minister Imran Khan over his alleged failure in handling the country’s economic crisis.

No one immediately claimed responsibility for the attack.

Two people were also wounded when the bomb, planted in a motorcycle, detonated Sunday afternoon in a vegetable market that had largely closed for the day, said Azhar Akram, a senior police officer in Quetta.

The market was several kilometers (miles) from where the political rally was taking place. Local TV footage showed several vehicles on fire following the blast, and Akram said explosive experts were examining the scene.

Cell phone service in Quetta had been suspended as a security precaution ahead of Sunday's rally, and additional security forces were deployed to the patrol the city, said Liaquat Shahwani, spokesman for the Baluchistan government. He said the opposition parties had been warned of the risk of violence.

Baluchistan province is famed for its gas and mineral wealth, and for decades, a low-level insurgency by armed groups has demanded more autonomy and a greater share in the region’s resources. Islamist militants also operate in the region.

Earlier this month, militants in Baluchistan killed 15 people when they ambushed a convoy of Pakistani oil and gas workers escorted by paramilitary troops.