Separatist gunmen shot and killed at least 22 people in southwest Pakistan on Monday in an attack that singled out ethnic Punjabis, government officials said.

Dozens of militants carried out the shootings early Monday in the district of Musakhail in impoverished Balochistan province, where security forces are battling sectarian, ethnic and separatist violence.

The Baloch Liberation Army (BLA), the most active militant separatist group in the province, claimed responsibility for the attack — one of the worst shootings in the region in the past several years.

The perpetrators stopped buses, vans and trucks one after the other on a highway connecting Punjab with Balochistan, Najibullah Kakar, a senior official in Musakhail, told AFP.

“The numbers of the militants were between 30 to 40. They stopped 22 vehicles,” he said.

“Vehicles traveling to and from Punjab were inspected, and individuals from Punjab were identified and shot.”

He said 22 people were killed, mostly Punjabi laborers, as well as two paramilitary soldiers.

Hameed Zehri, another senior official in the district, confirmed the death toll to AFP.

Balochistan is Pakistan’s poorest province, despite an abundance of untapped natural resources, and lags behind the rest of the country in education, employment and economic development.

Baloch separatists have in recent years intensified attacks on Pakistanis from neighboring provinces working in the region, as well as foreign energy firms they believe are exploiting its riches.

Punjabis are the largest of the six main ethnic groups in Pakistan, and are perceived as dominating the ranks of the military, which is locked in a battle to quash Balochistan’s armed factions.