The bomber was on foot and detonated explosives strapped to his body near the leader of a local council, Rahmatullah Turkistani, killing five civilians and injuring the official, a police commander told AFP.
Another 21 people were also hurt in the blast in in Khwaja Sabzposh district in Faryab province, provincial police Chief Abdul Khalil Andarabi said.
The apparent target was Turkistani, chairman of the Faryab provincial council, he said.
Separately, Nato's International Security Assistance Force (Isaf) said two foreign soldiers were killed on Thursday fighting insurgents in the south.
Southern Afghanistan is the heartland of the Taliban insurgency, though the militia have expanded their campaign to the once peaceful north.
The deaths, announced late Thursday, took to 619 the number of foreign soldiers killed in the Afghan war this year, the deadliest for the US-led military coalition since the toppling of the Taliban in late 2001.
The United States and NATO have more than 150,000 troops in Afghanistan fighting the Taliban-led insurgency, now in its 10th year.
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