A roadside bomb has killed 17 civilians, including four children, in western Afghanistan, police said, just days after a series of similar blasts killed nine people.

The bomb exploded on Tuesday under a trailer packed with villagers travelling to a ceremony in the Obi district of western Herat and was placed by Taliban insurgents, said Abdul Raouf Ahmadi, a police spokesman.

"There were 12 women, four children and one man among the dead. Seven others were wounded, including five children," Ahmadi said.

Violence in Afghanistan usually intensifies over the summer months. A senior Afghan general this week said insurgents had stepped up operations in the east near Pakistan as foreign troops continue to leave the country ahead of a 2014 withdrawal deadline.

Taliban office closed

Meanwhile, the Taliban have temporarily closed their office in Qatar, where it was hoped a peace deal would be brokered with the US and Afghanistan, blaming "broken promises", an insurgent official said on Tuesday.

"We have temporarily closed the Qatar office due to broken promises," a Pakistan-based Taliban official, who declined to be named, has told the AFP news agency by telephone.

"We are not happy with the Americans, the Kabul government and all parties who have not been honest with us."

Despite the row over the Taliban's office in Qatar, talks on their future role in Afghanistan are eventually likely to resume in what is expected to be a difficult and unpredictable peace process, diplomatic sources have said on Tuesday.