DHAKA: Bangladeshi troops stormed a cafe popular with foreigners in the diplomatic zone of the capital Dhaka after militants took dozens of diners hostage.

The siege ended on Saturday morning with six gunmen killed, 13 hostages freed and several casualties.

Here's what we know so far:

What happened?

Gunmen burst into a restaurant in the diplomatic quarter of the Bangladeshi capital Dhaka around 9:20pm on Friday night, as people were eating dinner.

They set off explosives, shouting “Allahu Akbar” (God is Greatest).

As a massive firefight broke out with police, the gunmen took up to 40 hostages, including many foreigners. Two police officers died in the gunfight.

Following a 10-hour stand-off, heavily armed commandos stormed the restaurant early Saturday morning, freeing several hostages.

Where did it happen?

The Holey Artisan Bakery restaurant is a western-style cafe popular for its large, leafy garden, situated on Road 79 in the capital's affluent Gulshan quarter.

The diplomatic zone is home to many of the city's expatriate workers and several foreign missions, as well as restaurants, upmarket malls and members' clubs.

The incident took place near the city's Nordic Club and the Qatar embassy.

Who is behind the attack?

About four hours after the attack the militant Islamic State (IS) group claimed responsibility, via an IS-affiliated news agency, Amaq.

It later issued a number of photographs of what it said were scenes from inside the cafe showing what appeared to be several bodies lying in pools of blood.

The news agency claimed that more than 20 people of different nationalities were killed.

Who are the hostages?

Little is known about the hostages, however, Italy's ambassador to Bangladesh Mario Palma told Italian state television that seven Italians were among the captives.

Sri Lanka said two of its nationals were among the hostages, but had been freed.

Tokyo said one Japanese was among those rescued, Jiji Press reported.

Is this kind of attack common?

The attack follows a series of murders of foreigners, religious minorities and secular activists in Bangladesh, blamed on or claimed by Islamist militants.

Cesare Tavella, an Italian aid worker was shot dead in Gulshan last September in an attack claimed by IS.

And in 2012 a Saudi Arabian diplomat was shot dead in the diplomatic zone.

However, Friday's attack appears to have been on a much bigger scale and the first time that people were held hostage.

The government and police deny that IS is active in Bangladesh and blame homegrown militants for the killings.