A suspected bomb outside a mosque in the Afghan city of Herat killed at least seven people and wounded 15 on Tuesday, police said, the latest casualties in a particularly bloody week in Afghanistan.

Officials in the western city believe explosives were hidden in a motorcycle left in a parking area outside the Jama Masjid, a large mosque dating from the 12th century, known for its intricate blue tiles.

Abdul Ahad Walizada, spokesman for Herat police, said at least seven people were killed and 15 wounded as they made their way to the mosque for prayers.

Near the border with Iran, Herat is one of Afghanistan's largest cities.

The attack came after a spate of violence in Afghanistan's capital, Kabul, where on Wednesday more than 150 people were killed and hundreds wounded in a suicide truck-bomb attack.

Several protesters were killed in clashes with police on Friday at the bomb site, and at least a dozen people were killed when suicide bombers attacked the funeral for one of the dead protesters on Saturday.