KABUL - A British security contractor and two teenage girls were killed Sunday when a Taliban insurgent rammed an explosives-laden car into a European Union police vehicle in Kabul, the latest attack of Afghanistan's fighting season.

At least 18 people were wounded in the assault, which comes three days after 14 people - mostly foreigners - were killed in a Taliban attack on a Kabul guest house that trapped dozens attending a concert.

The suicide bomber targeted the foreign convoy, which included at least two vehicles of the European Union Police Mission in Afghanistan (EUPOL), during the Sunday morning rush hour near Kabul airport.

"A suicide bomber detonated his Toyota sedan targeting a foreign forces convoy near Kabul airport today at 9:00 am," Kabul police spokesman Ebadullah Karimi told AFP.

"The target of the attacker was the foreign forces convoy. Two girls have died, 18 others are wounded, all of them civilians," he said, adding that three children were among those wounded.

The two girls, who the Afghan health ministry said were teenagers, are believed to have been passers-by at the time of the attack.

EUPOL in a statement confirmed that one of the mission's vehicles was hit by the explosion near Kabul airport resulting in the death of one personnel, with two other mission members suffering minor wounds.

In London, British Foreign Secretary Philip Hammond "strongly condemned (the Taliban's) cowardly actions".

"I can confirm that a British security contractor is among those killed in the attack," Hammond said in a statement. "His family has been informed and my thoughts are with them at this incredibly difficult time."

An AFP photographer at the scene saw troops hauling away the body of a person in military-style uniform, pulled out from the twisted wreck of a badly damaged sedan.

Taliban insurgents, who have stepped up attacks on foreign targets after launching their spring offensive late last month, claimed responsibility for the car bombing.

"A suicide attack was carried out on foreign forces near the gate of Kabul airport," spokesman Zabihullah Mujahid said on Twitter. On Friday the militant group justified its targeting of foreigners, saying that people from "invading countries" do not count as civilians.

"Every foreigner from an invading country especially NATO is considered an invader. We don't classify any of them as civilian," Mujahid said on Twitter.

Afghan forces are facing their first fighting season against the Taliban without the full support of US-led foreign combat troops.

Khalilullah Hodkhil, the deputy head of Wazir Akbar Khan hospital, said he had received the bodies of two young girls and 19 wounded people.

"All of them are civilians, including women and children," he told AFP.

"They are under treatment and their wounds are not life-threatening."

The attack came after NATO on Wednesday formally announced plans to retain a small military presence in Afghanistan after 2016 to help strengthen local security forces.

NATO Secretary General Jens Stoltenberg said the future mission would be led by civilians and "will have a light footprint, but... (with) a military component".

Afghan forces are now solely responsible for security after NATO's combat mission formally ended in December, with a small follow-up force staying on to train and support local personnel.

A Taliban suicide bomb hit a European Union police vehicle in Kabul in early January, killing at least one passer-by but not wounding any passengers.

The Taliban have waged a 13-year war to topple the US-backed government in Afghanistan. Official efforts to bring the insurgents to the negotiating table have so far borne little fruit.

The surge in attacks has taken a heavy toll on Afghan civilians, according to the United Nations Assistance Mission in Afghanistan (UNAMA).

In the first four months of 2015, civilian casualties from growing attacks jumped 16 percent over the same period last year, a recent UNAMA statement said.

Meanwhile, Taliban insurgents who kidnapped dozens of people in southeast Afghanistan early Saturday released most of them that night but at least two are still being held, officials said. The insurgents set up roadblocks in the Sayed Karam district of Paktia province, pulling passengers out of cars at gunpoint on suspicion they were government workers before taking them to an unknown location.

A total of 25 people who had been abducted were freed, interior ministry spokesman Sediq Sediqqi said on his Twitter account Sunday.