The violence began with blasts that ripped through a military camp in Pakistan’s Baluchistan Province late Sunday night, killing at least one soldier. Around the same time, armed men stormed into at least four police stations in the province, spraying bullets at officers and setting police vehicles on fire, local officials said.

By daybreak, militants had destroyed a bridge, bringing the major railway that runs across it to a halt. Then early Monday morning, the violence hit its apex when gunmen held up traffic on a major highway, shooting and killing nearly two dozen people.

Over a 24-hour period, the new wave of violence carried out by an armed separatist group has seized Baluchistan Province in southwestern Pakistan and left at least 38 people dead, worsening the country’s already deteriorating security situation.

The spate of coordinated attacks in Baluchistan began on Sunday, as the group, the Baluch Liberation Army, or B.L.A., announced that it was starting a new operation across the province. The B.L.A. is one of several insurgent groups that has demanded the province’s independence from the central government in Islamabad.

The deadliest single attack in the campaign so far unfolded in Musakhel, a district in Baluchistan, officials said, when armed men stopped traffic on a highway and demanded that passengers on buses and trucks show them their identity cards, officials said.

The gunmen forced some of the passengers out of the vehicles, and then shot and killed them, officials said. Nearly all of the victims were from Punjab Province, officials said, and the gunmen set at least 10 buses and trucks ablaze before fleeing the area.