Kyodo news agency, citing government sources, said the three were all women: Machiyo Narusawa, 66, from Tokyo, and Chiemi Miyazaki, 49, and Haruka Miyazaki, 22, who are believed to be a mother and daughter from Saitama prefecture.

The death toll was greeted with dismay in Japan, which is still reeling from the murders, by beheading, of two of its citizens in Syria earlier this year.