More than 1,000 ICE agents have left Minnesota after the Trump administration's controversial immigration enforcement operation that led to mass detentions, protests and the deaths of two US citizens.

US homeland security secretary Tom Homan said on Sunday that an undefined "small" force will stay for a short period to protect remaining immigration agents and keep investigating fraud allegations.

They will respond "when our agents are out and they get surrounded by agitators and things got out of control", Mr Homan told CBS.

"We already removed well over 1,000 people and, as of Monday, Tuesday, we'll remove several hundred more," and "get back to the original footprint [numbers]," Mr Homan said.

Thousands of officers were sent to Minneapolis and St Paul, known as the Twin Cities area of the state, for US Immigration and Customs Enforcement's (ICE's) Operation Metro Surge.

Launched on 1 December, the operation led to the arrest of more than 4,000 people, federal authorities said.

But the action has proved controversial. ICE agents, usually dressed in face masks and military-style camouflage gear, have repeatedly ⁠drawn angry demonstrations from residents.

Some protests have turned violent, with two protesters killed during confrontations.

Renee Nicole Good, 37, a mother-of-three, was shot dead in her car by an ICE agent early in January, purportedly acting in self-defence.

Alex Pretti, 37, an intensive care nurse, was wrestled to the floor by federal agents and shot multiple times in Minneapolis.

Local officials, including the city's mayor, Jacob Frey, and state governor, Tim Walz, have been fiercely critical of heavy-handed tactics that have seen ICE officers grab some people off the street and have made it clear they want them out.

Last week, Mr Homan said that more than 700 ICE agents would leave the state immediately, leaving more than 2,000 in the state. He said on Thursday that a "significant drawdown" was under way and would continue through this week.

Immigration enforcement will continue in the Twin Cities and there will be no end to mass deportations across the country, he added.

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Officers leaving Minnesota will report back to their stations or be assigned elsewhere.

Asked if future deployments could match the scale of the Twin Cities operation, Mr Homan said "it depends on the situation".

Operation Metro Surge was seen by some critics as an effort by Mr Trump to fulfil election promises to deport illegal immigrants and people without proper documentation.

ICE officers have also been deployed in cities such as Los Angeles and Chicago, where their presence has also attracted anger from officials and significant protests.