KABUL (Kyodo) -- Afghan police said Monday they have detained a total of six men in connection with the shooting death last week of a Japanese doctor who was a well-known aid worker in the central Asian country.
Tetsu Nakamura, local representative of Japanese aid group Peshawar-kai, and his staff were traveling in two vehicles when he was gunned down in an ambush Wednesday in the eastern province of Nangarhar, according to Afghan authorities and group members.
Seven to eight assailants -- with three armed with automatic rifles and other firearms -- were involved in the killing of Nakamura, 73, who was shot at close range with five bullets of a special kind not commonly seen in Afghanistan, the Afghan Interior Ministry said.
It appears the attack was planned for some time, possibly a year or two, a ministry official said.
Nakamura was in the first of two vehicles with a driver and a bodyguard when assailants in another car rammed into the side of his vehicle, forcing it to stop, according to the ministry and Peshawar-kai, a nongovernmental organization based in Fukuoka, southwestern Japan.
His car was being followed by a security vehicle carrying four people including local staff of the NGO.
Other assailants joined in the shooting from another car that came up from behind the security vehicle, the ministry said.
The 2003 recipient of the Philippines' Ramon Magsaysay Award, dubbed the Nobel Prize of Asia, Nakamura was known for dedicating his life to helping the Afghan people, especially for his work in developing an irrigation system and improving agriculture in eastern Afghanistan.
Afghan police initially said Nakamura and his associates were traveling in just one car but they later corrected the statement.
The police said they had not seen the second car at the shooting scene because the vehicle had to be used to carry the victims, including Nakamura, to medical facilities.
An Afghan health ministry official said Nakamura apparently bled to death.
A bullet which entered his right chest area and then lodged near the pelvis was custom designed for improved penetration, according to a doctor who performed the autopsy.
The doctor said such bullets are uncommon in the country.
Nakamura is believed to have been shot from above at close range while sitting in the front passenger seat.
Five Afghans, including the driver and bodyguards, were also killed in the attack.