Three bomb attacks have killed at least 13 people and injured 28 others in the Afghan city of Kandahar, according to a police commander.

The first blast, which took place on Tuesday morning, was set off by a suicide bomber riding an explosive-laden motorbike in the city centre, killing four children and one police officer, General Abdul Razaq, the provincial police chief told reporters.

Sixteen others including officers and civilians were injured in the attack, which was aimed at a mobile police post, he said. The Taliban claimed responsibility for the first attack.

"The attacker was on a motorbike in a crowded bazaar in Kandahar city near the border police mobile checkpoint. When police stopped him he detonated his explosives, killing five, including four children and one police," Razaq said.

In the early evening, two more blasts went off within minutes of each other at a central Kandahar intersection.

Provincial spokesman Faisal Ahmad said five civilians were killed, including a child, and three policemen died.

The latest blast, which no one has so far claimed responsibility for, happened just minutes after a smaller explosion, likely caused by an improvised explosive device, police said.

A doctor in the city's Mirwais hospital confirmed the casualties.

There are about 130,000 international troops in Afghanistan fighting the Taliban-led insurgency, with 91,000 of them from the United States.

The Taliban, toppled in late 2001 in a US-led invasion, are fighting against the government, with an increase in incidents of roadside bomb attacks and suicide explosions in recent years.

The latest deadly bombings comes as the Taliban confirmed that it was in talks to open a liaison office in Qatar with the mission of building peace talks with the Afghan government.

Source: Al Jazeera and agencies