WASHINGTON, June 2 — The US military is sharply increasing the number of National Guard forces in Washington and, in an extraordinary move, has readied active-duty troops outside the city to potentially respond to protests over the death of an African-American man in police custody, a senior defense official said yesterday.

The demonstrations, which have been largely peaceful but have turned violent after dark, have erupted across the country over the death of George Floyd, a 46-year-old black man who died in Minneapolis police custody after being pinned beneath a white officer's knee for nearly nine minutes.

US President Donald Trump said he was deploying thousands of troops in the nation's capital, whose mayor has been sharply critical of Trump's handling of the crisis.

The senior US defence official, who spoke on condition of anonymity, said all of the 1,200 National Guard forces in Washington had been mobilised and five states were sending 600 to 800 additional Guard troops who could be on the ground by evening.

A second defence official said some of the Guard troops were armed with lethal weapons.

Beyond that, active US military duty troops — including military police and engineering units — were on standby in the National Capital Region but outside the city itself and were ready to deploy if needed.

The hope, the first official said, was that the additional Guard units would make the use of active duty troops unnecessary.

"A decision to put active-duty troops on the streets would have to be made by the president at this point,” the official said.

US Defence Secretary Mark Esper, Army General Mark Milley, chairman of the Joint Chiefs of Staff, Attorney General William Barr and others would be at a Department of Justice to coordinate the response, the first official said. —Reuters