March 22, 2016 2:00 PM, EDT
US to Tighten Security for Air, Rail, Port Facilities in Wake of Brussels Bombings

The U.S. government is stepping up security measures in response to the March 22 bombings in Brussels as President Barack Obama pledged to do "whatever is necessary" to help bring the perpetrators to justice.

Security will be tightened at airports, rail stations and ports in the U.S. in response to the deadly attacks in Belgium, according to a government official briefed on the plan.

The U.S. Department of Homeland Security is expected to make an announcement late March 22, said the official, who wasn’t authorized to disclose the plans and asked not to be identified.

The stepped-up security includes assigning additional law enforcement personnel to the facilities, the official said. Some of the measures won’t be publicly disclosed because they are classified, according to the official.

Brussels became the latest European city to be targeted in a terrorist attack as three coordinated blasts killed at least 31, injured more than 230 and deepened the sense of crisis across the continent.

Obama, on a visit to Cuba, said the U.S. would support Belgium in bringing those responsible for the March 22 attacks to justice, and called on the world to unite against terrorism.

“We must be together regardless of nationality or race or faith in fighting against the scourge of terrorism,” Obama said at the beginning of a speech in Havana. “The thoughts and the prayers of the American people are with the people in Belgium and we stand in solidarity with them.”

After explosions ripped through the Brussels airport and a subway station on March 22, authorities there went on high alert, and the U.S. embassy advised Americans in the country to shelter in place.

Obama was briefed on the attack by U.S. national security officials, and he spoke with Belgian Prime Minister Charles Michel by phone to offer his condolences. Obama offered assistance in investigating the attacks and bringing those responsible to justice, and pledged the full cooperation and support of the U.S. in the fight against terrorism, the White House said.

The New York City Police Department said it had deployed additional counterterrorism resources to crowded areas and transit locations across the city, and was working with federal authorities to monitor the situation. The transit system in Washington said it was increasing canine sweeps and patrols as a precaution. Both agencies said they weren’t aware of any direct threat to their cities.

The Department of Homeland Security issued a statement saying it was monitoring the situation in Brussels and would take additional security measures if they were needed.

DHS, which oversees agencies including the Transportation Security Administration that handle domestic anti-terrorism activities, is coordinating with its European counterparts, the agency said. Citizens are also encouraged to report any activity they think is suspicious.

Airports, which share responsibility for police and security duties with TSA, also increased their vigilance. Atlanta’s Hartsfield-Jackson International, the world’s largest airport, went on “heightened alert” following the attack, according to a press release. It didn’t specify what steps were being taken.