Two men, one of them British, were shot dead in the centre of Kabul yesterday amid rising tension caused by a series of attacks including the assassination of a British charity worker.

David Giles, 42, from Hull, and Jason Bresler, a South African, worked for DHL, the international courier company and were arriving at the company’s offices in the morning when the shootings took place. An Afghan security guard was also killed.

There was confusion over who carried out the killings. The interior ministry said one of the locally employed security guards killed the two westerners before shooting himself. A source in the presidential palace, however, said another guard had killed all three victims before fleeing.

David Walker, chairman of Saladin, the British security company that protected DHL’s base and employees, said its guards had been closely vetted during recruitment.

The Taliban denied any involvement, but that would not rule out involvement by another antiwestern group led by Gulbuddin Hekmatyar, who claimed responsibility for the deaths of 10 French soldiers killed south of the capital in August.

The killings underlined the increasing danger in Kabul amid concern in Washington and London that President Hamid Karzai is not capable of asserting his authority even in the capital.

They followed Monday’s murder of Gayle Williams, a charity worker who held joint British and South African nationality, by two Taliban terrorists on a motorcycle. The Taliban said Williams, 34, who worked for the Christian charity Serve, was shot dead “because she worked for an organisation which was preaching Christianity in Afghanistan”.

Phil Malcolm, a friend of Giles in Kabul, said yesterday he was “an amazing friend to all who knew him”.

Giles’s ex-wife, Julia Wilson, with whom he had a 10-year-old son, James, said from her home in Hull: “I am just deeply shocked. He is my son’s father. I just can’t believe what happened.”

In a message posted on Bresler’s Facebook internet page, Jaco Davidson, one of his friends, wrote: “You were a pillar of strength and someone I always relied on to be there for me and be true to me no matter what. I will remember you for always for all the good you brought to my life.”

Gillian Westaway, another friend, said: “You never lost me Jason . . . I lost you . . . you made me feel alive . . . I will miss you forever.” Security has deteriorated across Afghanistan in recent months with the Taliban apparently able to pick off “soft targets” at will, even within the capital.

Meanwhile, paratroopers returning from the south of the country have given graphic accounts of the brutal fighting in which they have been engaged since early summer.

The 2nd Battalion, the Parachute Regiment, lost 10 men.

Soldiers from its C Company have described an ambush in which a patrol of 80 men lost two men dead and others wounded.

“We were hit by a wall of fire,” said Corporal Matthew “Des” Desmond, 31, in charge of the lead platoon. He was speaking last week after the company’s return to its base in Colchester, Essex.

“It was the best-initiated ambush I have seen in 13 years of being in the army. They [the Taliban] were brilliant that day.”

In total, five of 2 Para’s dead were from C Company. In return, they killed an estimated 300 of the enemy – who have nicknamed Helmand the “mouth of hell” – in more than 90 battles and skirmishes.

On Sunday, June 8, a suicide bomber blew himself up beside a British patrol a mile from the base, killing three paratroopers. Four days later, during an operation deep inside Taliban-controlled territory, the C Company patrol was approaching a river when it came across children playing. “[They] were laughing and joking and were pointing in the direction that we were going. We didn’t realise it at the time but they were pointing at the place we were about to be ambushed.”

A few minutes later, with all 80 British troops within their arcs of fire, the insurgents attacked.

It was not clear whether the children were deliberately directing the paras into danger.

Lance Corporal James “Jay” Bateman, 29, and Private Jeff “Doc” Doherty, 20, were both killed instantly with shots to the head and neck.

Additional reporting: Miles Amoore in Kabul

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