KABUL — At least 21 Afghan police officers were killed in three simultaneous Taliban assaults Monday night in northern Afghanistan. Although civilians were nearby, security forces fired artillery rounds to repel the militant advances.

The hours-long attack focused mostly on overtaking oil wells and vehicles near the capital in Sar-e Pol province, officials said, as the Taliban bids to demonstrate power and undermine government control during peace talks to end the 17-year-old war.

Militants used rifles and rocket-propelled grenades in the assault, which also injured at least 23 police officers, Zabihullah Amani, a spokesman for the provincial governor, told The Washington Post on Tuesday.

“The areas are with the government, but they are under range of Taliban fire,” Amani said. “We still have not received any assistance.”

Three senior security officials — an intelligence officer and two police commanders — were killed in the attacks, said Mohammad Noor Rahmani, provincial council chief.

Afghan forces fired Soviet-era D-30 howitzers to repel militants on the capital outskirts, Amani said. The Associated Press reported this forced civilians to flee, although officials said there were no reports of civilian casualties.

The Taliban, which asserted responsibility for the attack, suffered casualties in the assault, Amani said. But officials have not said how many militants were killed or wounded.

The assault joins a stream of near-daily Taliban strikes designed in part to exert pressure during peace negotiations between the militants, the United States and regional powers. Militants infiltrated a government building in Kabul on Dec. 24, killing 29 people.

Analysts have said President Trump’s sudden announcement that he would withdraw about half of the 15,000 U.S. troops stationed in Afghanistan would strengthen the Taliban’s negotiating position as Afghan forces struggle to maintain security, suffering record-high casualties in 2018.

There are signs those attacks will continue through the winter, a time the Taliban historically has used to rest and regroup in Pakistan through bitterly cold months, said Khalid Pashtun, a lawmaker in Kandahar.

“This year we have noticed they’re staying inside Afghanistan,” he said, adding that it was possible Afghan forces have been caught off guard after expecting assaults to become less frequent.

Monday’s attack also may have been a bid to claim territory to further undercut Islamic State militants mustering in the north, he said. In August, more than 150 Islamic State fighters surrendered to government forces after battling the Taliban in neighboring Jowzjan province.

Government forces also have battled Islamic State militants; the latest offensive came Tuesday in eastern Nangahar province, in which 27 Islamic State fighters were killed, the AP reported.