Afghan security forces inspect the site of a deadly bombing in Jalalabad, east of Kabul, on Sunday. (Mohammad Anwar Danishyar/AP)

An explosion at a funeral in Afghanistan's eastern province of Nangahar on Sunday killed at least 17 civilians, officials said.

The government said the blast, in the city of Jalalabad, was caused by a suicide bomber who blew himself up as mourners offered prayers for a former district chief in the province, which lies near the border with Pakistan. But a later report suggested a bomb may have been detonated remotely, the Associated Press reported.

The casualties included several tribal chiefs. The target of the attack was not immediately clear. The Taliban insurgents who spearhead the insurgency against Afghan and U.S.-led troops in the country denied having a link to the attack.

No other group has claimed responsibility for the bombing, which also wounded 14 people.

Some tribal chiefs in Nangahar have been behind an effort to raise a force of local civilians to protect their community from affiliates of the Islamic State, which have gained ground in the province despite repeated operations by the government and U.S. troops in recent months.

Last summer, suicide bombers blew themselves up at a Kabul funeral for the son of a politician, where senior government leaders had gathered. A group of mourners lost their lives in the attack, but the leaders survived it.

The Islamic State asserted responsibility for that strike, as it did following an attack Thursday on a pro-Iranian cultural center in the capital, which killed nearly 50 people and wounded scores of others.

That was the third attack claimed by the Islamic State in less than three weeks.

The expansion and escalation of attacks by the network have caused anxiety among Afghans and raised questions about the ability of the government and foreign troops to quell the growth of the violence.

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