QUETTA, Pakistan (AP) — A roadside bomb targeting a police vehicle in volatile southwestern Pakistan on Monday killed at least four people and wounded 18 others, mostly civilian pedestrians, a government spokesperson said.

The attack happened in Quetta, the capital of Baluchistan province, said Babar Yousafzai, a spokesman for the provincial government. He said the dead included two police and two civilians.

In a statement, the outlawed Baluchistan Liberation Army claimed responsibility for the attack. The BLA, which was designated a terrorist group by the United States in 2019, said its fighters targeted the vehicle of a police officer who was behind the arrest of members of the group.

Although such attacks are common, t he Pakistani Taliban have also stepped up assaults on troops and police across Pakistan since November, when they ended a monthslong cease-fire with the government.

Pakistan has also been battling an insurgency in Baluchistan for more than a decade, with separatists in the province demanding complete autonomy or a larger share of the province’s gas and mineral resources.

Monday's attack in Quetta comes days after Pakistan said its top intelligence agency arrested Gulzar Imam, who is also known by the name Shambay, and was the militant founder and leader of another banned group, the Baluch Nationalist Army. The BNA is an umbrella group for Baluch insurgents formed after two main insurgent groups merged: The Baluch Republican Army and United Baluch Army.

In separate statements, Pakistan's Prime Minister Shahbaz Sharif and Baluchistan chief minister Abdul Qudoos Bizenjo condemned the attack. They asked authorities to provide the best possible medical care to the wounded.

The Pakistani Taliban, who are known as Tehreek-e-Taliban Pakistan, have claimed previous such attacks in Baluchistan and elsewhere. The militant group is separate from, but allied with, the Afghan Taliban.

The latest attack comes a day after the TTP shot and killed two police officers in Quetta. One of the assailants was also killed when police returned fire after coming under attack in the city Sunday night.