At least 60 militants have been killed in fighting between the Taliban and a rival Islamic group, Hezb-e-Islami, in northern Afghanistan, police say.
The fighting in Baghlan province erupted on Saturday morning. A number of civilians died in the crossfire.
The rivalry between former allies seems to concern control of local villages and taxes, a BBC correspondent says.
Afghan officials also said dozens of Hezb-e-Islami fighters had defected to the government during the fighting.
Hezb-e-Islami, loyal to former PM Gulbuddin Hekmatyar, is the second biggest militant group in Afghanistan.
The two groups have previously been allied in their opposition to Afghan's central government and foreign forces.
Baghlan's police chief told the BBC that 40 Hezb-e-Islami fighters had been killed, as well as 20 Taliban militants.
The Taliban are said to have detained at least 50 members of Hezb-e-Islami, Gen Akhbar said.
Some Hezb-e-Islami militants were surrounded by Taliban forces, a regional police spokesman, Laal Mohammad Ahmadzai, told the AFP news agency.
He said 11 Hezb-e-Islami commanders and 68 of their men had defected to the government.
Estimates of the number from other Afghan officials ranged between 50 and 100.
Fighting is taking place in an area where the Afghan government has little or no presence on the ground, says the BBC's Chris Morris in Kabul.
The US labelled Gulbuddin Hekmatyar a "specially designated global terrorist" in 2003.
His mujahideen faction was one of the groups that helped end the Soviet occupation of Afghanistan.
In the unrest that followed in the early 1990s, his group of fundamentalist Sunni Muslim Pashtuns clashed violently with other mujahideen in the struggle for control of Kabul. Mr Hekmatyar served twice as prime minister during that period.
Hekmatyar's forces are usually allied with the Taliban
Hezb-e Islami was blamed for much of the terrible death and destruction of that time, which led many ordinary Afghans to welcome the emergence of the Taliban. They forced Mr Hekmatyar and his men to flee Kabul in 1996.
After the Taliban were overthrown, he pledged allegiance to the new Western-backed administration in Kabul. However, after an alleged anti-government plot by Hezb-e Islami was uncovered, the group took up arms and allied itself to the Taliban.
Although his position has been weakened in recent years, he remains a key figure in the insurgency, especially in the east and parts of the north.