(Reuters) - A Massachusetts district attorney plans to bring state murder charges against Dzhokhar Tsarnaev, who has been sentenced to death in a federal trial for a deadly bomb attack on the 2013 Boston Marathon, her office said on Saturday.

The Boston Globe reported that Middlesex District Attorney Marian Ryan said she would charge Tsarnaev with murdering MIT police officer Sean Collier and for other crimes in the aftermath of the marathon attacks.

Ryan said a guilty verdict in Massachusetts could keep Tsarnaev in prison if he successfully appeals his federal convictions.

"When you come into Middlesex County and execute a police officer in the performance of his duties and assault other officers attempting to effect his capture, it is appropriate you should come back to Middlesex County to stand trial for that offense," Ryan said in a statement.

Critics have said a prosecution is Massachusetts would be expensive and unnecessary, given the death sentence dispensed in federal court.

Other state charges could include carjacking and kidnapping, the newspaper report said.

Tsarnaev was convicted in April of killing three people and injuring 264 in the bombing near the finish line of the world-renowned Boston Marathon in 2013, as well as fatally shooting a police officer three days later.

The same jury voted for execution by lethal injection in May, placing him on federal death row. Massachusetts does not have the death penalty.

At his formal sentencing on June 24, the 21-year-old ethnic Chechen apologized and admitted he and his now-dead older brother carried out the attack.

Tsarnaev filed a motion in federal court on Monday seeking a new trial, according to court records.