— The authorities in Bangladesh
began a broad effort on Wednesday to compile a list of young men who have disappeared and may have been recruited by militant groups for terrorist operations like last week’s massacre of 22 people at a restaurant in the capital, Dhaka.
The attack was the deadliest in a series of murders since 2013, which initially targeted atheist bloggers but later also included foreigners, minorities and gay activists. The authorities have blamed local militant groups, although the Islamic State, also known as ISIS or ISIL, and a regional branch of Al Qaeda have taken credit for many of the killings. The Islamic State claimed responsibility for last weekend’s assault as it was underway, and released a video late Tuesday night warning that the attacks would not stop until an Islamic government was established.
The police were setting up checkpoints around the city and said that anyone sharing, uploading or commenting favorably on jihadist activities online would face punishment. They also began what they described as a huge effort to focus on young people who have disappeared in recent months, like the men who carried out the 11-hour siege last weekend. All of them had vanished between December and February, family members and the police said.
The Islamic State’s warning, in English and Bengali, heightened fears in Dhaka, which has been on high alert since the killing of 20 hostages in the restaurant, most of them foreigners, and two police officers. The nearly six-minute video, released on Twitter and the Telegram app, warned of more attacks to come.
“What you witnessed in Bangladesh yesterday was a glimpse,” a militant said in the video, made public by the SITE Intelligence Group, which monitors jihadist websites. “This will repeat, repeat and repeat until you lose and we win.”
Law enforcement officials struggled with how to get word out to families about the importance of reporting the sudden disappearance of young male relatives, a senior intelligence official said.
The father of one of the attackers made an impassioned plea to other parents to keep an eye on their children and protect them from jihadist recruitment. “I request all parents give more time to their children, give more attention to their children,” said the father, Imtiaz Khan Babul, a former Dhaka politician, choking up as he spoke.
Mr. Babul, a physical education teacher, said that after his son, Rohan, vanished in late December, he met several other parents whose boys had also disappeared. “One of the parents was a former army officer, and I can tell you all of the missing sons were from well-established, educated families,” he said. “One was a judge, another a banker.”
Mr. Babul, 58, berated himself for failing to recognize warning signs, saying, “I feel I am a failed father.”
The attackers included three young men from elite backgrounds, including Mr. Babul’s son, and two from low-income families in the northern part of the country, the police said. The three young men from affluent families had been reported missing, but the lower-income families had not filed reports, a police officer involved in the investigation said.
The officer said the lower-income families had assumed that their sons, who had left home to live in Dhaka, had gone off in search of work and fallen out of touch.
The senior intelligence official said he had no estimate of how many families had reported young men missing because there was no centralized system for gathering the reports. But he said that would change under a new procedure.
Mr. Babul said Rohan — a top student, football player and chess player — had been studying business at BRAC University, a private school in Dhaka, when he disappeared.
Mr. Babul and his wife were on a trip to India when their son left home at 10 p.m. on Dec. 30, carrying a bag, he said. He conducted a frantic search, he said, going to numerous law enforcement agencies, none of which could help him find his son.
“I’d like to apologize to the families who lost their near and dear ones in the restaurant,” Mr. Babul said. “I also apologize to the nation.”
New details of the weekend’s attack were supplied by one of the hostages, a woman who asked that her name not be used because the police had ordered her not to speak to reporters.
She said she had survived because she was among eight people whom the attackers believed to be Bangladeshi Muslims and gathered at a single table, saying not to worry, that their lives would be spared. Among them were two children, 8 and 13, the woman said.
The attackers told the group to keep their heads down and they would be safe, the woman said, adding that the 20 hostages who were killed were shot and then hacked to death with knives within a half-hour after the siege began.
The terrorists urged those they had spared to cover the children’s eyes and ears during the killings, but it was impossible for them not to understand what was going on, she said.
After it was over, the attackers turned off the lights, she said, and the hostages at her table sat with their heads down in the dark for hours.
The attackers seemed to grow nervous as morning approached because they could not decide what to do with the surviving hostages, the woman said. They took two men from the group onto the roof to discuss what to do with them and the others. The woman said she learned later that one of the men had persuaded the attackers to keep their promise to spare the Bangladeshi Muslims.
And so, at around 6 a.m., one and a half hours before the army stormed the restaurant to end the siege, the attackers released the people at her table, she said. As they left the building, law enforcement officers leapt onto one of the men who had been involved in the rooftop discussions, apparently believing that he was part of the militant group, “and it was like they were going to kill him,” she said.
The man was taken into custody for questioning and held at least through Tuesday, the police official involved in the investigation said.
Since her release, the woman said, she has not been able to sleep. When she closes her eyes, she said, she sees the militants’ shadows on the wall and hears the sounds of their footsteps.