NEW YORK — A man inspired by Islamic State extremists strapped on a crude pipe bomb, slipped unnoticed into the nation’s busiest subway system and set the device off at rush hour Monday in a scenario that New York has dreaded for years, authorities said.

In the end, the only serious wounds were to the suspect, Akayed Ullah, a 27-year-old Bangladeshi immigrant and former cab driver, authorities said. But the attack sent terrified commuters fleeing through a smoky passageway, and three people suffered headaches and ringing ears from the first bomb blast in the subway in more than two decades.

“This was an attempted terrorist attack,” Democratic Mayor Bill de Blasio said. “Thank God the perpetrator did not achieve his ultimate goals.”

In Washington, President Donald Trump said the explosion highlighted the need to change immigration policies, including the type of family-based visa Ullah obtained to come to the U.S. in 2011. Such visas are “incompatible with national security,” the Republican president said in a statement.

“America must fix its lax immigration system, which allows far too many dangerous, inadequately vetted people to access our country,” said Trump, who campaigned on cracking down on immigration.