TOKYO -- The Japanese government on late Monday confirmed seven Japanese were killed in a hostage crisis in Algeria, local media reported.

Japanese Prime Minister Shinzo Abe made the announcement at a meeting of a task force on the issue, adding three Japanese nationals are still unaccounted for.

Abe said that it was "extremely regrettable" that the deaths had been confirmed and strongly condemned the terrorism attack is "despicable" and "unforgivable," Kyodo News Agency reported.

Abe asked officials to take every possible measure to gather information so as to confirm the whereabouts of the three missing Japanese.

He also said Japan will continue to seek cooperation with the international community to combat terrorism.

The victims were among 10 Japanese employees of the Japan Gasoline Company (JGC) who went missing after Islamic militants seized a natural facility in southeast Algeria last Wednesday.

A total of 17 Japanese were at the gas plant when the abduction took place and the JGC earlier has confirmed seven Japanese nationals out of the 17 are in safe condition.

Meanwhile, the death toll of foreigners in the crisis rises to 37, according to report.