KABUL: An Afghan police officer was killed and another three wounded on Thursday when a suspected suicide bomber they were following detonated the explosives in his vehicle, an official said.

“A suicide bomber was trying to enter Kabul with the intention of detonating explosives in a crowded part of the city,” said Hashmat Stanekzai, spokesman for the Kabul provincial police chief.

“He was being followed by police.”

The chief of Kabul's provincial police, Abdul Rahman Rahimi, said the blast occurred after police stopped the car.

The Taliban issued a statement to media claiming responsibility.

Afghan authorities regularly claim to have thwarted attacks on the capital as the insurgents concentrate on government, military and foreign targets.

Five foreigners have been killed in the past month in attacks on soft targets such as a French-run school last week, where a German aid worker was killed.

The US-led international combat mission, which peaked in 2010 with 140,000 American and Nato troops, ends on Dec 31.

Afghan security forces will assume full responsibility on Jan 1, with a residual international force of around 13,000 to provide training and support.

The head of Afghanistan's intelligence service said the drawdown of foreign troops had made it more difficult to track down militants.

Under pressure to explain the rise in attacks on Kabul, Rahmatullah Nabil, chief of the National Security Directorate, told parliament on Wednesday that the removal of manpower and technology by withdrawing foreign forces had contributed to the spike in violence.

In Helmand province, he said, 65 surveillance balloons had been removed with the closure of US and British bases last month.

“Now I have just six agents working there,” Nabil said.

He said there were 107 terrorist cells in the provinces surrounding Kabul, but the city relied on a security strategy that was up to 40 years out of date.