ISLAMABAD, PAKISTAN - Unknown gunmen have killed a Japanese aid worker and his five colleagues in eastern Afghanistan.

Officials said the deadly shooting took place Wednesday morning in Jalalabad, the capital of Nangarhar province.

A provincial government spokesman told VOA that slain Dr. Tetus Nakamura and members of the Japan Medical Services (JMS) non-governmental organization were traveling to a project site when they came under attack.

Attaullah Khogyani said that Nakamura, the head of the non-governmental organization, was "seriously" wounded and taken to a city hospital where he succumbed to his injuries. His Afghan driver and several security guards were among those killed, he added.

Japanese Prime Minister Shinzo Abe paid tribute to Nakamura's long career in Afghanistan, telling reporters in Tokyo it was "very shocking" to learn of his death.

The U.N mission in Afghanistan condemned and expressed its "revulsion" at the killing of Dr. Nakamura. "A senseless act of violence against a man who dedicated much of his life to helping most vulnerable Afghans," it said.

The Taliban in a brief statement denied involvement in the attack that killed the 73-year-old Japanese medical doctor and his colleagues. Both Taliban insurgents and militants linked to the Afghan branch of Islamic State terrorist group operate in Nangarhar.

Eyewitnesses told VOA at least three assailants took part in the attack and managed to flee.

Afghan President Ashraf Ghani recently awarded Dr. Nakamura honorary citizenship of Afghanistan for a decade long service as the head of the Japanese charity in Nangarhar. He had arrived in the country after his Japanese predecessor was abducted and killed.

Wednesday's attack comes more than a week after a U.S. national working for the United Nations was killed in the Afghan capital of Kabul.

No one claimed responsibility for the November 24 attack.