In the aftermath of a bloody weekend attack carried out by young men, several from prosperous families, the prime minister renewed official entreaties to parents and school administrators to inform the authorities about unexplained and prolonged absences by young men.

“I urge the guardians to take steps to bring back their missing sons home,” she said. “We will give them all cooperation to find their missing boys and for their treatment, if necessary.”

More details emerged about the attack on the religious gathering on Thursday.

About half an hour before morning prayers were to begin, a group of men approached a police checkpoint at a high school near the prayer ground and set off a bomb, said Tofazzal Hossain, an assistant superintendent of the Kishoreganj police. “They attacked the police out of nowhere,” said Mr. Hossain, who added that some of the attackers had been carrying guns and bladed weapons.

Six other officers were seriously wounded, said a police inspector, Mueid Chowdhury, but they were expected to survive. Several civilians were also hurt.

The police killed one of the attackers and arrested two others, Mr. Hossain said. A search was underway for the other assailants.