The deaths of the other two missing Japanese were confirmed earlier.
They were among the 17 Japanese nationals, all employees of the Japanese engineering firm JGC Corp., who were among hostages including other foreigners taken by Islamist militants on Jan. 16 after attacking the In Amenas gas plant in the Sahara region of the North African country. The other seven survived.
The plant is a joint venture operated by Britain's BP, Norway's Statoil and Algeria's state-owned energy company.
Japan's chief government spokesman Yoshihide Suga announced the death of the latest victim, Kyodo News reported.
Japan Times quoted Suga as saying a team of Japanese officials in the Algerian capital identified the 10th Japanese victim from among dozens of bodies of unknown nationalities brought from the gas complex.
Kyodo said Japanese police planned to conduct autopsies to determine the precise cause of the deaths of the 10 victims.
Three non-Japanese workers of the company still remained unaccounted for, the report said, quoting the company.
The hostage crisis ended last Saturday after Algerian military forces stormed the plant, resulting in the deaths of many foreign hostages and their captors.
On Monday, Algerian Prime Minister Abdelmalek Sellal said the dead included 37 from eight countries, including three Americans, and 29 abductors.
Separately, Kyodo reported a government plane carrying the bodies of the other nine Japanese victims and the seven survivors arrived Friday in Tokyo. The body of the 10th victim will come by another plane.
"The Japanese government resolutely condemns the terrorist group responsible for this despicable act of terrorism," Prime Minister Shinzo Abe told a crisis-response meeting at his office, after being briefed by his officials who returned from Algeria, the report said.
Abe also asked his officials to examine the hostage crisis under the direction of Chief Cabinet Secretary Yoshihide Suga to ensure the safety of Japanese nationals and firms overseas.
The government is under considerable pressure to release basic information on the entire hostage incident because of its magnitude and the confusion surrounding it.
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