Getty ImagesDr Nakamura headed a Japanese charity and served in rural areas of AfghanistanA Japanese doctor who devoted his career to improving the lives of Afghans has died, after being injured in an attack in eastern Afghanistan.
Gunmen shot Tetsu Nakamura, 73, while he was travelling in a car to monitor a project, officials say.
Five Afghans were also killed in the attack, which happened in the city of Jalalabad.
Dr Nakamura headed a Japanese charity focused on improving irrigation in the country.
In October this year, he was awarded honorary citizenship from the Afghan government for his humanitarian work.
No-one has yet said they carried out the attack and the motive remains unclear.
Japanese Prime Minister Shinzo Abe said he was "shocked" by the death of Dr Nakamura while the US embassy in Kabul condemned the shooting, saying "aid workers are not targets".
The United Nations Assistance Mission in Afghanistan (UNAMA) expressed its "revulsion" over the killing.
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Attacks of this kind are fairly common in Afghanistan.
Last week, a US national working for the UN in Afghanistan was killed in a blast targeting a UN vehicle.
Research by the BBC found an average of 74 men, women and children were killed every day in Afghanistan in the month of August alone.
How did the attack unfold?
Dr Nakamura was travelling in a vehicle in Jalalabad city in the eastern province of Nangarhar on Wednesday morning when he came under attack.
He was shot on the right side of his chest and was in the process of being transferred to a hospital near the capital Kabul when he died at Jalalabad airport, officials told AFP news agency.
His three security guards, a driver and one of his colleagues were also killed, said Attuallah Khogyani, a spokesman for Nangarhar's governor.
Photos from the scene showed a white pickup truck with at least three bullet holes in its windscreen.
ReutersBullet holes are seen in the window of the vehicle
AFPThe victims were in a white pickup truckWho was Tetsu Nakamura?
He was born in the Japanese city of Fukuoka in 1946.
After qualifying as a doctor he moved to Pakistan in 1984 to treat patients with leprosy.
Two years later, he headed to Afghanistan, where he opened his first clinic in a remote village in Nangarhar and established a non-governmental organisation, Peace Japan Medical Services (PMS).
AFPDr Nakamura has been recognised for his workAt its peak, PMS operated 10 clinics providing help for leprosy patients and refugees amongst others.
Dr Nakamura had also heavily been involved in the construction of wells and irrigation in villages where many suffered from cholera and other diseases because of a lack of clean water.
In 2003, he won the Ramon Magsaysay Awards, widely regarded as the Asian equivalent of the Nobel Prize.
In 2014, Dr Nakamura told news outlet the Japan Times he had taken a different route to work each day to ensure his safety.
However, he also added that the best precaution he could take was to "befriend everyone".
"I've tried to make no enemies... The best way is to befriend everyone, even if that makes people think I lack principles. Because the people are the only thing I can depend on there," he said.
"And that's surprisingly more effective than carrying a gun."
What has the reaction been?
A spokesman for Afghan President Ashraf Ghani said the government strongly condemned "the heinous and cowardly attack" on Afghanistan's "greatest friend".
"Dr Nakamura dedicated all his life to change the lives of Afghans, working on water management, dams and improving traditional agriculture," Sediq Sediqqi wrote on Twitter.
The Dutch ambassador in Kabul, Ernst Noorman, called the killing "senseless", saying Dr Nakamura had dedicated his life to the "peace and development of Afghanistan".
The governor of Nangarhar province, Shah Mahmood Meyakhail, said "all the people of Nangarhar" were saddened by Dr Nakamura's death and were thankful for the many years he spent helping the people, Tolo News reports.
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