A Bangladeshi woman shows a photo of her missing son, who worked at a cafe that was the scene of an attack and seige in Dhaka, Bangladesh. (AFP/Getty Images)

One by one, the young men went missing.

The son of a prominent local leader disappeared from Dhaka on Dec. 30. A college student was last seen Feb. 3. A high school student never made it to his tutoring session Feb. 29. Ultimately, five young men vanished.

The men — some from Bangladesh’s privileged elite — resurfaced July 2, when the news agency of the Islamic State released photographs of the Dhaka terrorists wearing head scarves, toting automatic weapons — and grinning.

In the days after the devastating siege of a popular cafe in Dhaka that left 23 dead, including two police officers, Bangladesh has begun looking for its lost sons.

Worried family members have posted pictures of missing youths on social media, in local newspapers, in a private Facebook group called “Desperately Seeking Missing Persons (Bangladesh).”

A desk in Meer Saameh Mubasheer’s room at his family’s home in Dhaka, Bangladesh. Mubasheer, 18, was one of the cafe attackers. (Mohammad Ponir Hossain/Reuters)

“No family with children between 13 and 25 should feel secure, because people of these ages are vulnerable,” said Meer Hayet Kabir, the father of one of the attackers, who had spent frantic weeks searching for his son.

Police said this week that at least 10 young men — many from well-connected families — were missing and suspected of being caught up in militant groups. Another 18-year-old man, a kitchen assistant at the cafe bakery who had been detained after the siege as a possible suspect, died at a hospital late Friday. His family has alleged he was tortured in police custody.

The government asked YouTube to purge clips from radical preachers and issued warnings about sharing jihadist messages on social media. Bangladesh’s prime minister, Sheikh Hasina, gave an emotional appeal Thursday for parents to inform the police about their missing boys. Investigators launched a nationwide effort to learn more about the missing and whether any had been recruited for militant groups.

Meanwhile, investigators are examining airline and port records to see whether the cafe attackers left the country — possibly under false names — for training overseas.

“They belong to one of the local groups of radical Islamists who have been engaged in violent activities for some time, and it is also now increasingly evident that they had forged some links or connections with some international terrorist groups as well, including the Islamic State,” said Gowher Rizvi, a senior adviser to Hasina. “The forensic investigation will throw more light.”

Although secular bloggers, religious minorities and foreigners have been killed in a series of attacks that worsened in the past year, Rizvi’s comments are a shift from the government’s long-held position that the attacks are the work of local militants acting alone, or of Hasina’s political opponents.

Bangladesh, a Muslim-majority country of about 160 million, has grappled with Islamic extremism since its independence from Pakistan after a war in 1971.

A number of countries were the target of serious terrorist attacks in the last week, including Iraq, where a car bomb in a Baghdad shopping district killed at least 187 people. (Deirdra O'Regan/The Washington Post)

Hasina, who has maintained her grip on power after a flawed 2014 election in which the opposition did not participate, has pursued extremists — especially those connected to her rivals — with zeal. Five opposition politicians have been executed for war crimes by a controversial tribunal since 2013. Some analysts believe political instability and repression in Bangladesh is fomenting radicalism.

In 2013, a group of progressive youths demanding capital punishment for the war criminals provoked militants to hack a blogger to death with a cleaver. More than a dozen bloggers, secularists and minorities have suffered the same fate, with an al-Qaeda-inspired militant group claiming responsibility for the killings.

Last year, the Islamic State asserted responsibility for several acts of violence, including the killing of a Japanese agricultural worker and an Italian aid worker, stoking fears among the expatriate community.

“It’s almost like this is ground zero for a jihadist showdown in South Asia,” said Lisa Curtis, a senior research fellow at the Heritage Foundation. “This latest attack has to jolt the Bangladesh government out of their complacency.”

But little official evidence has emerged that these global terror groups had operational linkages — transfers of resources, technology or training — with local groups, according to Ajai Sahni, a terrorism expert and executive director of the Institute for Conflict Management in New Delhi. The terrorists at the Dhaka cafe did send photos of bloodied bodies to a private Islamic State-linked email account during their operation, and the pictures were immediately uploaded, he said.

Sahni said that groups such as the Islamic State do most of their recruiting online, so it is no surprise that well-educated youth like the cafe attackers would be swept up that way. Investigators are poring over their social-media accounts for clues. A controversial Islamist preacher is under fire in India after reports that one of the attackers, Rohan Imtiaz, the son of a politician from Hasina’s Awami League party, quoted him on his Facebook page.

Another attacker, Meer Saameh Mubasheer, 18, was last seen Feb. 29 after he left his elite English-immersion school, Scholastica, to go to a tutoring center. Police said closed-circuit camera footage showed him getting out of his car before he reached the center and hopping into a rickshaw.

His father, a telecom executive, said in an interview that his quiet son was interested in religion but was not rigorous, sometimes skipping prayer. He rarely had friends over and lived a protected life, driven around town by a chauffeur.

Mubasheer was an average student who loved sketching and playing guitar, but he stopped doing both a couple of months before he went missing. He also deactivated his Facebook account.

“ ‘Are you happy that I will not be wasting my time?’ ” Kabir recalled his son telling him, a bit mockingly, when the father quizzed him about it. The parents were relieved, thinking he might have more time to study for his June exams.

Looking back, Kabir could not detect overt warning signs, but he remains haunted by an eerie phone call that the boy received on the day he left, believing he was summoned somewhere.

Over the past two years, a substantial number of young men have gone missing in Bangladesh, said Sakhawat Hussain, a retired brigadier general and security analyst.

Some have traveled to Syria, police say, while others have returned to recruit locally. Tuesday, the Islamic State released a video featuring three Bangladeshi men, based in Raqqa, Syria, who vowed more attacks, according to the SITE Intelligence Group, a monitoring service.

Police say they have identified medical representatives of pharmaceutical companies, Islamic teachers and traders who have recruited followers through social-networking sites and blogs, as well as face-to-face contact. Initially, they may read the teachings of the prophet Muhammad together or chat, but “once they see interest, they devote more time nursing them,” said Sanwar Hossain, a counterterrorism official.

Investigators said that those they have arrested in the past — including an engineer and a former teacher at an English-language school — rented apartments in Dhaka to provide recruits with both theoretical and practical training.

Gowen reported from New Delhi. Rama Lakshmi in New Delhi contributed to this report.