One person has died and two others are injured after being shot by a suspected sniper at an immigration facility in Texas, officials say.

The shooter is also dead from a self-inflicted gunshot wound after the incident in Dallas, said Homeland Security Secretary Kristi Noem.

The attack unfolded on Wednesday morning at a detention centre for US Immigration and Customs Enforcement (ICE).

The incident follows a string of attacks on ICE facilities across the US in recent months.

The motive or targets of the attack are unclear. Fox News quoted officials as saying no law enforcement officers had been injured.

"While we don't know motive yet, we know that our ICE law enforcement is facing unprecedented violence against them," Noem said. "It must stop."

Dallas police said on X: "The preliminary investigation determined that a suspect opened fire at a government building from an adjacent building.

"Two people were transported to the hospital with gunshot wounds. One victim died at the scene. The suspect is deceased."

Preliminary information suggests a sniper carried out the shooting from outside the facility and hit victims in a "secure detainee location", Acting ICE Director Todd Lyons told CNN.

He said three individuals were "down", including the suspected shooter.

"We're not sure on their condition," Lyons said.

The ICE field office in Dallas has been targeted by a series of protests this summer.

A justice department official told the BBC's US partner CBS that there was a bomb threat in late August at the facility. A suspect was arrested.

Last month shots were fired at ICE offices in San Antonio, Texas, in what investigators described as a "targeted attack" against federal employees.

No injuries were reported in that incident, which ICE blamed on "political rhetoric" and "misinformation" about the Trump administration's detention policies.

Another shooting occurred on the 4 July public holiday at an ICE facility in Alvarado, Texas, after a protest escalated into a faceoff with police. An officer was shot in the neck, and survived.

US Vice-President JD Vance posted on X on Wednesday: "The obsessive attack on law enforcement, particularly ICE, must stop. I'm praying for everyone hurt in this attack and for their families."