Alex Pretti, a 37-year-old nurse, was shot and killed by US immigration officers on Saturday during a protest. Several videos show officers opening fire on him while he was on the ground.

The shooting sparked bipartisan condemnation in the United States and protests in Minneapolis, capping months of escalating violence in which masked, unidentified and heavily armed Immigration and Customs Enforcement (ICE) and Border Patrol agents have grabbed people suspected of violating immigration laws off the streets.

"I haven't seen all of the details, but what I have seen is obviously concerning," Starmer told reporters aboard a plane bound for China, where he arrived Wednesday for an official visit.

Pretti was carrying a firearm for which he held a permit, but no video shows him with the weapon in his hand.

"I don't think anybody could see some of the footage and not say it's concerning, but I'm not claiming to have seen all the footage and all the detail, but of what I have seen, I'd say it's concerning," Starmer said.

Pretti's death occurred less than three weeks after that of Renee Good, a 37-year-old mother-of-three who was shot and killed on January 7 in Minneapolis by an ICE agent.

Facing outrage over Pretti's death and his administration's initial comments blaming the victim for the incident, US President Donald Trump said Tuesday he would "de-escalate a little bit" in the city.

The president has also spoken with local Democratic authorities, and a portion of the 3,000 federal agents dispatched to Minneapolis is expected to leave the city soon.