The taking of hostages by gunmen in Dhaka's diplomatic quarter is the latest in a string of attacks that have sparked international alarm.

The United States and Bangladesh have promised more cooperation against violent extremism in the Muslim-majority nation.

But the two governments still tiptoe around whether transnational terror groups like the Islamic State group are involved in the mounting bloodshed, which has included a wave of killings of liberals, foreigners and religious minorities.

The identities of those who attacked the Dhaka cafe late Friday were not immediately known.

IS and al-Qaida affiliates have claimed responsibility for many of the previous attacks, typically by smaller groups of machete-wielding assailants, that have claimed nearly two dozen lives since 2013. The frequency of attacks has increased in recent months.