KABUL — Distressed Afghans held vigils Thursday to mourn a beloved Japanese doctor who transformed barren swaths of eastern Afghanistan and spent decades caring for the sick, and to demand justice for his murder.

Tetsu Nakamura, 73, was shot to death on Wednesday in Jalalabad, the main city in the eastern province of Nangarhar where he had worked since the 1980s.

He was killed along with five Afghan guards and colleagues in an attack no-one has yet claimed, and which the Taliban condemned.

Even in a country inured to brutal violence and daily bloodshed, Nakamura's killing came as a horrifying shock to many Afghans.

In Kabul, more than 100 people from across Afghan society held a candlelit vigil for Nakamura, holding signs calling him a "true hero".

"Dr Nakamura was an icon of humanity," said Hekmat, who only uses one name, an activist at the vigil.

"He was here for the kids and for many years to serve the Afghan people and provide them a sustainable livelihood."

Nakamura had devoted 35 years of his life to healing Afghans and Pakistanis and eventually became an honorary citizen of his adopted home.

Nakamura had also issued stark warnings of the dangers of desertification in Afghanistan, and his organization built wells and irrigation canals that changed dusty expanses of Nangarhar into green, tree-lined fields.

"Every year, it gets worse. I know that the people in Afghanistan are scared of losing their country that will become a desert," he told Japanese broadcaster NHK last year.

According to Japanese news agency Jiji Press, Nakamura's family members were en route to Afghanistan from the western Japan city of Fukuoka.

His wife and eldest daughter are expected to return home with his body next week, Jiji reported.

Vigils were held in other provinces including Nangarhar and Parwan north of Kabul, while social media were flooded with an outpouring of grief. At least one person had written a song to commemorate Nakamura.

But behind the sadness was a palpable sense of anger.

The Afghan government has recently boasted of dislodging Islamic State jihadists from the territory they held in Nangarhar, but Nakamura's death highlights the woeful state of security that persists there and across Afghanistan.

"We demand the government of Afghanistan to bring the perpetrators to justice ASAP," one banner at the Kabul vigil read.

Nakamura's murder came days after an aid worker for the UN was killed in a bombing in Kabul.

On Nov. 24, Anil Raj, an American who worked for the UN Development Program in Afghanistan, died when his vehicle was targeted. — AFP