"We are making every effort to determine the fate of those seven people. The situation is very difficult. That causes a bitter regret," Abe told reporters, as cited by Kyodo news agency.
On Friday, the Islamic State terrorist group claimed responsibility for taking hostages inside a cafe located in Dhaka's diplomatic quarter. According to the latest data, the attack has left 20 people dead, while 13 hostages have been rescued by the country's security forces. Most of the victims are foreigners, according to reports.
Japan's Foreign Ministry sent anti-terror experts to Bangladesh over fears that Japanese nationals may be among hostages taken in Dhaka. The Japan International Cooperation Agency (JICA) reportedly said it had not been able to contact eight of the Japanese 68 staff it employs in the Bangladeshi capital.
One Japanese citizen who was later rescued from the restaurant has received a gunshot wound, while the remaining seven, including two women, are still missing.