Afghan President Hamid Karzai speaks during a news conference in Kabul February 26, 2012. (MOHAMMAD ISMAIL/REUTERS)

President Hamid Karzai on Sunday urged Afghans to avoid violent retaliation for the burning of a pile of Korans at the main U.S. military base in Afghanistan last week and called for the punishment of those behind the act, which sparked nationwide protests.

Karzai also voiced his support for NATO’s decision Saturday to recall its personnel from Afghan ministries after two U.S. service members were killed by an Afghan security official in the country’s heavily protected Interior Ministry earlier in the day. Karzai described the move as “temporary” and justifiable in the face of the attacks and spreading protests.

Meanwhile, officials in the northern Kunduz province said residents took part in fresh demonstrations Sunday, attacking a police station and a U.S. military base. At least 16 policemen and a half-dozen U.S. service members were wounded in the attacks, in which protesters used a hand grenade and small arms fire, according to Sarwar Hussaini, a spokesman for Kunduz’s governor.

Several protesters were wounded during clashes with police, he said.

The deaths at the ministry in Kabul — by a man wearing an Afghan police uniform — follows Thursday’s assassination of two U.S. troops by an Afghan soldier during protesters’ attack on a U.S. base in the east.

More than 25 Afghans have died in the demonstrations, and the service members’ killings prompted London to pull its civilian advisers from Afghan ministries, according to British media.

During days of demonstrations across the country, many protesters pushed for the withdrawal of foreign troops from Afghanistan and chanted slogans against the United States and Karzai.

Protesters and Afghan Islamic clerics have demanded the parliament and government to put those responsible for the Koran burnings on trial. The resurgent Taliban has urged Afghans to ignore apologies from U.S. authorities over the apparent inadvertent act and urged retaliation against Western installations and military personnel.

However, Karzai, while pushing for the punishment of those responsible for Koran burning, has called on his countrymen to not resort to violence because he said the insurgents and their foreign backers would manipulate their protests.

“Now is the time to return to calm and not let the enemies of peace and development to use this situation,” Karzai said in a news conference Sunday.

“We have asked for justice and punishment for those who have done this act,” he said of the culprits behind the Koran burnings.

The week’s events have exposed a core vulnerability of the Obama administration’s strategy for winding down the decade-long Afghan war and are seen as a blow to the West’s effort in winning the hearts and minds of Afghans.

NATO leaders are scheduled to hold a summit in May in Chicago, where they had hoped to finalize details of the withdrawal and the gradual handover of security responsibilities to Afghan forces, as well as report on progress in negotiations with the Taliban.

The escalating tension here prompted apologies for the Koran burning from President Obama and several top U.S. defense officials. But demonstrations continued unabated over the weekend.

Special correspondent Sayed Salahuddin contributed to this report.