The doctor, well-known in Japan, had been shot on the right side of his chest and was in the process of being transferred to a hospital in Bagram near Kabul when he died at Jalalabad airport, officials said.

The five Afghans killed were three of Nakamura’s security guards, a driver and another colleague, Khogyani said.

A spokesman for Afghan President Ashraf Ghani called Nakamura “one of the closest friends of Afghanistan”.

He “dedicated his life to helping and cooperating with our people”, spokesman Sediq Seddiqi said.

Japan Prime Minister Abe said he was shocked at Nakamura’s death.

“I was shocked that he had to die this way,” Abe told reporters, adding that the Afghan people had thanked Nakamura for his contributions.

The attack comes as humanitarian groups remain on high alert just days after an American aid worker for the UN was killed in a bombing in Kabul.

In a statement condemning Wednesday’s incident, the UN Assistance Mission in Afghanistan expressed “revulsion” at Nakamura’s killing.

It was “a senseless act of violence against a man who dedicated much of his life to helping” Afghanistan’s most vulnerable, UNAMA said.

Freed teacher details hellish 1,200 days as a Taliban hostage

Mitsuji Fukumoto, an official with Nakamura’s organisation, told reporters in Tokyo that the motive for Wednesday’s attack was unclear.

“We have no idea what was the reason behind the attack, whether it was a simple robbery or whether it was conflict of interest,” Fukumoto said.

Nakamura was famous in Japan for his aid work, which dates back decades.

Peshawar-kai was founded by associates of Nakamura, who had lived and worked in Afghanistan and Pakistan since 1984 when he went to treat leprosy patients among Afghan refugees.

In 2003 Nakamura, a native of the southwestern Japanese city of Fukuoka, won the Philippines’ Ramon Magsaysay Award for peace and international understanding – often called Asia’s Nobel Prize.

Fond of sporting Pashtun dress, Nakamura was an outspoken opponent of the 2001 US-led war that ousted the Taliban regime, whom he defended as able administrators.

Jalalabad resident Auzubillah, who only uses one name, said he heard shooting at about 8am (03:30 GMT).

“I saw there were gunmen attacking a Japanese and his security guards,” he said. “Then the gunmen left the area through a small street.”

Photos from the scene showed a white pickup truck with a large cabin. Its side windows appeared to have been shot out, and at least three bullet holes could be seen in the windscreen.

The Taliban denied responsibility for the attack, saying they have “good relations” with organisations that “contribute to the reconstruction of Afghanistan”.

Authorities recently claimed the jihadists have been territorially defeated in the province – but small cells are thought to remain.

Aid agencies and non-governmental groups are sometimes targeted in Afghanistan’s war.

On November 24, Anil Raj, an American who worked for the UN Development Programme in Afghanistan, was killed when his vehicle was targeted in a bombing in Kabul.

Also in the capital, the Taliban in May targeted Counterpart International, a US-funded non-profit group working with marginalised people. Nine people were killed in that attack.

Additional reporting by Reuters