KABUL: A suicide bomber blew himself up in the midst of worshippers concluding prayers marking a key Muslim festival in northern Afghanistan, killing six people including two local police commanders, officials said on Sunday.

The bomber struck as worshippers were exiting a mosque in Baghlan province's Old Baghlan City and were congratulating each other on the start of the Eid al-Adha, the Feast of the Sacrifice, said Lal Mohammad Ahmadzai, spokesman for the regional police commander in the north.

Ahmadzai said at least 20 other people were wounded in the blast, which occurred in the city's Hassin Tal village.

Among the six people killed were two local police commanders, said Kamen Khan, the police chief in Old Baghlan City.

One of them was a well-known local leader named Abdul who, like many Afghans, goes only by one name.

There was no immediate claim of responsibility, but the Taliban, against whom Nato has waged a decade-long war, routinely target Afghan officials and security forces as well as international forces.

Separately, Nato said that one of its service members was killed following an insurgent attack in the south on Saturday.

The death raises to 494 the number of coalition troops killed in the country so far this year. Nato provided no other details.

As the US-led coalition and its Afghan partners have focused their operations on Taliban strongholds in the south and east, the insurgency has carried out an increasing number of attacks in the north and west.

The two police officials killed are the latest victims of assassinations in northern Afghanistan, which is heavily populated by minority ethnic groups such as the Tajiks, Uzbeks and Hazaras.

These groups have been resistant to President Hamid Karzai's US-backed plans to reconcile with the Taliban, who are made up mostly of Pashtuns, the majority ethnic group in Afghanistan.

Five leaders affiliated with the Northern Alliance, a coalition mostly composed of non-Pashtun minorities which has fought the Taliban since 1996, have also been slain in a little over a year. They included Gen. Daud Daud, an ethnic Tajik who oversaw police activities in nine Northern provinces; as well as three provincial police chiefs and one provincial governor.

Minorities already worry that President Hamid Karzai, a Pashtun, will make too many concessions to their Taliban enemies to shore up his Pashtun base.

Whatever support for peace talks that Karzai has won from minority groups is likely to erode if militants continue to pick off their leaders one by one.