About 20 people, including two district police chiefs, have been killed in Taliban attacks in Afghanistan as fighting rages in the war-torn country, authorities said Sunday.

On Sunday morning, three Taliban militants were killed, and two militants, one Afghan Local Police (ALP) constable and a civilian were wounded during a clash at an ALP checkpoint in Archi district of northern Kunduz province, ALP commander in Archi Mohammad Amin told Xinhua.

Two of the slain militants had recently been freed from Kunduz provincial jail on parole, Amin added.

Two Taliban militants were killed and one police officer wounded after they attacked a police checkpoint with guns in Nahri Saraaj district of southern Helmand province earlier on Sunday.

Four Afghan police officers, including a district police chief, were killed in an improvised bomb explosion in Sarobi, a district in Afghanistan's eastern Paktika province.

"On Saturday night, Darya Khan Talash, police chief of Sarobi, and three district police officers were martyred following an improvised bomb explosion along a road in Sarobi," provincial police spokesman Shah Mahmoud Arian told Xinhua.

A police vehicle was destroyed, he said, adding, "The martyred police officers were on the way to a scene where Taliban militants attacked a security checkpoint in surrounding areas of Sarobi. They were part of a unit of responding police."

The deceased police chief had served as police officer in ranks of Afghan National Police for 18 years.

In southern Zabul province, similar to Sarobi attack, Sahib Jan, police chief of Naw Bahar district and one police officer were killed and six police personnel wounded in two separate incidents on Saturday.

"Sahib Jan was martyred and four police wounded following a Taliban improvised bomb explosion in Shahr-e-Safa locality of Zabul. One police officer was killed and two wounded in Zabul's Shamulzay district," local TV channel Tolo News reported.

Taliban militants have frequently used the tactic by initiating an attack and targeting responding groups of security forces by improvised bombs or direct ambushes.

In a separate development, three pro-government militiamen and three Taliban militants were killed, and three fighters and a militant were wounded during clashes at a security checkpoint in Qara Bagh district of eastern Ghani province Saturday night, Wahidullah Jumazada, spokesman of the provincial government, told Xinhua.

Also on Saturday evening, three civilians were killed, and eight civilians and one policeman wounded after a Taliban rocket struck near a district office building of Tagab district in eastern Kapisa province, Shahiq Shorash from the provincial police told Xinhua.

In early March, Afghan President Mohammad Ashraf Ghani issued a decree to release 5,000 Taliban inmates on parole, and the Taliban agreed to release 1,000 soldiers. The exchange of prisoners was part of a peace deal inked between the Taliban and the United States in Qatar in February.

More than 4,400 Taliban prisoners and over 840 Afghan security forces have been released by the two sides so far.

Afghan leaders, including President Ghani, have frequently demanded the Taliban reduce violence and agree to a ceasefire since February.

The militants, however, have intensified fight-and-run attacks, killing and injuring scores of servicemen and civilians.

In the meantime, Ghani and Chairman of High Council for National Reconciliation Abdullah Abdullah held a telephone discussion with U.S. National Security Adviser Robert O'Brien on Friday, discussing security issues and the need to urgently start peace talks between the Afghan government and the Taliban, reported local Ariana News TV.

O'Brien was quoted in the report as saying the United States supported a united, sovereign and democratic Afghanistan that will not become a safe haven for terrorism.