A Bangladeshi employee at the Dhaka cafe where 20 customers, including seven Japanese, were ruthlessly slain has said the Japanese were killed almost immediately.

In an exclusive interview in the capital, the man, who wished to remain anonymous for fear of his own life, said he was hiding in a cold room with a "young" Japanese man who was later shot while he was able to escape.

The man, who was working at the Holey Artisan Bakery in the upscale section of the city on July 1, said he had gone to get ingredients for a pasta dish from a chiller inside the restaurant when he heard the screech of "Allahu akbar!" and shots ring out.