US President Donald Trump renewed his call for implementing hardline measures on immigration, including vetting, a day after a blast triggered by an Islamic State-inspired Bangladeshi-origin man near a metro station in New York City left four people injured.

The New York bomber was inspired by the Islamic State and the Christmas attacks the outfit inspired in Europe — France and Germany.

Akayed Ullah, the 27-year-old suspect of Bangladeshi origin who is in police custody, has told investigators he chose the underground tunnel of the New York subway to trigger the bomb strapped to his body, a low-tech device based on a pipe bomb, because of Christmas posters there.

Ullah set off the device around 7:20 am in the underground tunnel of the New York City underground at the Port Authority Bus Terminal near the iconic Times Square as commuters passed through on their way to work. He himself was injured severely, while four people suffered minor injuries.

New York City officials described the incident as an “attempted terrorist attack”. The explosion was caught on surveillance cameras in the tunnel that showed the bomber walking with other commuters.

The department of homeland security said in a statement that the “suspect was admitted to the United States after presenting a passport displaying an F43 family immigrant visa in 2011. The suspect is a Lawful Permanent Resident from Bangladesh who benefited from extended family chain migration”.

Trump said the suspect’s arrival in the US through the extended “family-based chain migration was incompatible with national security” and pointed to his travel ban as a step forward in “securing our immigration system”.

“First and foremost… America must fix its lax immigration system, which allows far too many dangerous, inadequately vetted people to access our country. Congress must end chain migration,” he said, adding that it must also act on his other proposals to increase the number of Immigration and Customs Enforcement officers, enhancing the arrest and detention authorities for immigration officers and end fraud and abuse.

Ullah had arrived in the United States from Bangladesh in 2011 and Saifullo Saipov, the Manhattan truck terrorist, had come from Uzbekistan in 2010 and was on Green Card. Trump cited both these to call for “the urgent need for Congress to enact legislative reforms to protect the American people”.

Ullah came to the US on an F43 visa, issued to him through his family connection to an American citizen.

The American immigration system allows citizens to apply for certain relatives — spouses, children, parents, siblings and their spouses and minor children — to be allowed to come and live in the US. The visas fall under different preferences, or categories; siblings of US citizens come in the fourth preference, the F4, and their children come under F43s.

Since a law change in 1965 loosened what had been a very restrictive system, America’s immigration policy has been based around giving preference to people with advanced education or skills or those with family ties to US citizens.

What that has meant is that as immigrants from places like Asia and Latin America started coming to the US in larger numbers and became citizens, they applied for their family members to join them. Once naturalized, those brought in were able to then sponsor their own relatives.