Nine Italians were among 20 foreign nationals killed in Friday's attack by suspected Islamist militants at a cafe in Bangladesh, Italy's foreign minister has said.

Security forces stormed the restaurant in Dhaka and ended a 12-hour standoff on Saturday, killing six gunmen.

"We have identified nine (Italians) killed, there is another person who is missing and could be hiding himself or could be among wounded people ... we are looking for him," Foreign Minister Paolo Gentiloni told reporters.