New Delhi: Police were questioning family members of five attackers who stormed an upscale restaurant in Dhaka’s diplomatic zone and killed police officers and hostages before they were fatally shot by security forces over the weekend, an officer said Wednesday.

The police officer said parents and relatives of the five young Bangladeshi men were questioned Tuesday and some again on Wednesday. The officer declined to give details and spoke on condition of anonymity as he was not authorised to talk to reporters.

The officer also said authorities have freed three of five former hostages they had been holding for questioning. Authorities were looking into the backgrounds of these people and questioning their families and friends.

Police have eight people in custody, including one described as an attacker, but no one has been arrested as a suspect.

Two police officers and 20 hostages — nine Italians, seven Japanese, an Indian and three students at American universities — were killed. Thirteen hostages were rescued when security forces stormed the restaurant Saturday morning. Authorities said security forces, civilians and some hostages were injured but have not given details.

The bodies of the Italian and Japanese victims were returned to their home countries Tuesday.

The hostage siege was the worst of recent militant attacks in Bangladesh, after previous killings were carried out by young men wielding cleavers and machetes and targeting atheists and other individuals accused of being enemies of Islam. The escalation has raised global concerns about whether the South Asian country can cope with increasingly strident Islamist militants.

Meanwhile, Daesh has warned of repeated attacks in Bangladesh and beyond until rule by its strict version of Sharia is established, saying in a video last week’s killing of 20 people in a Dhaka cafe was merely a glimpse of what is to come.

Five Bangladesh militants, most from wealthy, liberal families, stormed the upmarket restaurant on Friday and murdered customers, the majority of them foreigners, from Italy, Japan, India and the United States, before they were gunned down.

“What you witnessed in Bangladesh ... was a glimpse. This will repeat, repeat and repeat until you lose and we win and the Sharia is established throughout the world,” said a man identified as Bangladeshi fighter Abu Eisa Al Bengali, in the video monitored by SITE intelligence site.

Bangladesh has rejected the Daesh’s claim of responsibility for the Friday attack and blamed it on a domestic militant group.

It was one of the deadliest attacks in Bangladesh, where Daesh and Al Qaida have claimed a series of killings of liberals and members of religious minorities in the past year.

The government has also dismissed those claims.

The Daesh video began with pictures of recent attacks in Paris, Brussels and Orlando in the United States that the Middle East-based militants have claimed.

The fighter in the video, who spoke in both Bengali and English, said Bangladesh must know that it was now part of a bigger battlefield to establish the cross-border “caliphate” the group proclaimed in 2014.

“I want to tell the rulers of Bangladesh that the jihad you see today is not the same that you knew in the past,” he said from a busy street in the militant group’s de facto capital of Raqqa, in Syria.

“The jihad that is waged today is a jihad under the shade of the Caliphate.” Though Bangladesh has rejected the Daesh claim of responsibility for Friday’s attack, police said they were stepping up security in response to the video threat.

“We are taking this issue seriously. All our concerned units are working tirelessly,” said deputy police inspector general Shahidur Rahman.

Police believe the domestic Jamaat-ul-Mujahideen Bangladesh, which has pledged allegiance to Daesh, played a significant role in organising the band of privileged, educated young men who carried out the attack.

Police have said they are hunting for six members of the group suspected to have helped the attackers.