Following intelligence warning, the government Sunday night beefed up security measures at the three international airports in the country, officials concerned said.

Apart from restricting visitors, authorities of the airports asked their security personnel to remain vigilant and increase monitoring in and outside the airports.

"We stepped up security from last night [Sunday night]," Capt MK Zakir Hassan, director of Hazrat Shahjalal International Airport, told The Daily Star.

He said they had done so after receiving intelligence information and that vigilance had been strengthened through CCTV at all the entrances.

The airport will be under closer supervision, said the director.

Another source claimed that a US team of security personnel arrived in Dhaka Sunday, which might have prompted the authorities to step up security measures at the airport.

Security has been beefed up at Sylhet Osmani International Airport since yesterday morning with the deployment of additional members of police and Armed Police Battalion.

"We have taken special security measures following instructions from the high-ups Sunday night," said Chief Security Officer Nazrul Islam of the airport.

He said the internal security personnel were asked to remain alert.

In the port city, authorities of Shah Amanat International Airport closed off its visitor gallery Sunday night.

It was part of the special security measures, airport manager Wing Commander Rezaul Karim said.

The police also increased vigilance in the port city, said Abdul Jalil Mondal, commissioner of Chittagong Metropolitan Police.

"The measure has been taken considering the overall situation of the country," he told The Daily Star. "Law enforcers have been told to remain alert everywhere."

The alarm at the country's major airports came after the murders of two foreign nationals recently and early Saturday's bomb attack at Hossaini Dalan.

The measure also came against the backdrop of foreign countries maintaining security alert for their citizens in Bangladesh since the murders of Italian national Cesare Tavella on September 28 and Japanese Kunio Hoshi five days later.

Four weeks into the murder of Hoshi, three improvised bombs were blasted at Hossaini Dalan in Old Dhaka prior to bringing out Tazia procession, killing one teenager and injuring 87 others.