The suspect accused of killing UnitedHealthCare CEO Brian Thompson has pleaded not guilty to New York state murder and terrorism charges.

Luigi Mangione, 26, appeared in court on Monday to be arraigned on 11 state criminal counts, including murder a crime of terrorism.

He also faces federal stalking and murder charges that could lead to a death penalty sentence.

Prosecutors allege that Mr Mangione shot Mr Thompson in central Manhattan before going on the run. Authorities later arrested him at a McDonald's in Pennsylvania.

Mr Mangione is facing 11 state criminal counts in New York, including first-degree murder and murder as a crime of terrorism.

If convicted of all the counts, he would face a mandatory sentence of life in prison without the possibility of parole.

In court on Monday, Mr Mangione appeared wearing a maroon sweater, white collared shirt and khaki pants.

In addition to a long stream of journalists waiting for him to appear members of the public - almost all of them young women - were in court, some of whom told CBS, the BBC's US partner, that they were there to show their support.

Federal prosecutors have also separately charged Mr Mangione for using a firearm to commit murder and interstate stalking resulting in death. Both charges could make him eligible for the death penalty.

He has yet to enter a plea on those charges.

Prosecutors have said the federal and state cases will move forward parallel with one another.