Gunmen in restive southwestern Pakistan shot and killed at least 20 workers early Saturday at a dam construction site, the deadliest recent attack targeting civilians in a region facing a low-level insurgency, authorities said.

The violence targeted the Gobdan area of the Turbat district in southwestern Baluchistan province, a region where nationalist and separatist Baluch groups have fought against the Islamabad-based government for years. However, no group immediately claimed responsibility for the attack in Pakistan, a country that faces a deadly Taliban insurgency and threats from other Islamic extremists.

A large group of gunmen attacked a labor camp near the dam construction site, overpowering eight security guards on the site and shooting dead sleeping laborers before fleeing, government commissioner Pasand Khan Buledi of the Makran division said. Buledi gave the casualty figure and said the attack wounded three people.

Buledi said 16 of the dead were from Pakistan's Punjab province and four were from Sindh province. He said the eight guards, all from Baluchistan, were unharmed in the attack.

Previous separatist attacks saw gunmen kill people from Punjab province, Pakistan's most populous province, over what they describe as its exploitation of their region. Those from Baluchistan often are let go.

Baluchistan Home Minister Sarfaraz Bugti told private satellite news channel Geo TV that Pakistan's paramilitary Frontier Corps was searching in the nearby mountains for the attackers.

"We will chase them down and brought them to justice," Bugti said. "We need help in this war against terrorists. Alone, we cannot fight."

Baluchistan government spokesman Jan Mohammad Buledi said the government would offer the families of the deceased 1 million rupees (nearly $10,000) each.

Baluchistan is the scene of a low-intensity insurgency by separatists who want substantial share of revenue from gas and mineral resources and complete autonomy from Islamabad. Islamic militants also operate in the area.

Baluch and human rights activists say Pakistani forces detained their people for years without bringing them to court, sometimes killing them and dumping their bodies in the desert. Three years ago, the Voice for Baluch Missing Persons organization handed the United Nations a list of 12,000 names they said belonged to people missing in the conflict.

The disappearances in southwestern Baluchistan province began swelling in the mid-2000s, when Gen. Pervez Musharraf's government cracked down on insurgents there. The government repeatedly has denied the allegations, with some saying many of the missing were criminals in hiding, had joined militant groups or had been abducted by others.

Saturday's violence was the deadliest recent attack to target civilians in the region. In September 2012, 10 laborers and five tribesmen in a labor camp were gunned down in the province's Khuzdar district.