A suicide bomber on a motorcycle detonated explosives in an Afghan district close to the border with Pakistan, killing at least 10 people including children, officials said on Saturday.

The attack comes one day ahead of a NATO summit in Chicago, where the coalition intends to spell out its role in Afghanistan after foreign combat troops leave by the end of 2014.

"The bomber blew himself up in a crowded market and it was powerful," said Sardar Mohammad Zazai, police chief of eastern Khost province.

He said the assailant was heading for a police checkpoint in the Ali Sher district along the border with Pakistan's "lawless tribal areas".

No one claimed responsibility for the attack, which killed six children, one civilian adult and three policemen.

Eleven years into the NATO-led war against the Taliban, the Islamist group holds large sway in Afghanistan's restive south and east, where they enjoy enormous popular support.

Afghan security officials have said they expect this year's summer fighting season to be bloody as the third phase of a security handover from NATO to Afghan forces gets underway.