Afghans from all walks of life have expressed sorrow over the killing of Japanese aid worker Tetsu Nakamura by unknown armed men and condemned it in its strongest term.

Nakamura, head of aid agency Peace Japan Medical Services, had been badly injured and five of his local colleagues were killed in an attack by unidentified armed men on Wednesday in the eastern Nangarhar's provincial capital Jalalabad city.

Nakamura later succumbed to his injuries at hospital.

Afghans have described the aid worker as a philanthropist that was involved in humanitarian activities in the eastern region of the war-battered country, and denounced his assassination as enmity with humanity especially with the people of Afghanistan.

"Nakamura was a hero, a philanthropist because he had left his prosperous life in Japan to serve the poor and war-weary Afghans," Jalalabad resident Shir Wali told Xinhua Friday.

"He (Nakamura) was involved in providing humanitarian assistance to the people, but unfortunately he was killed in Nangarhar where hundreds of people have benefited (from) his humanitarian projects," 35-year-old Kabul resident Aga Gul told Xinhua.

Afghan President Mohammad Ashraf Ghani awarded honorary citizenship to Nakamura in October for his services to Afghanistan, according to media reports.

The Japanese aid worker had helped construct a number of water dams and canals, besides building health clinics and mosques in the eastern region, according to Amin Shah, a resident of Nangarhar province.

"His objective was to help Afghans and contribute in the rebuilding process of Afghanistan," he told local media.

Afghans have also denounced the killing of Nakamura on social media as a crime against Afghans and humanity.

"It is a matter of sorrow to kill a person who wants to rebuild your country. Peace-loving Afghans will always remember you for your services here," Farid Behboud said on Facebook.

"Both the government and the people of Afghanistan as part of paying last respect should see off the coffin of the late Nakamura at Kabul airport," Afghan Bashir Ahmad Ghazali posted on his Facebook.