Boston Marathon bombing suspect Dzhokhar Tsarnaev, 19, has been indicted on charges of killing four people and using a weapon of mass destruction.

He faces 30 charges linked to the April 15 terror blasts, which killed three and injured more than 260 others. Seventeen of the charges could bring life in prison or even the death penalty, US prosecutors said.

A fourth victim, a policeman, was shot dead by Tzarnaev and his brother Tamerlan, 26, while authorities tried to hunt them down, according to federal prosecutors.

Tamerlan Tsarnaev was killed in a shoot-out with police days after the double blasts.

The explosives were described as pressure-cooker bombs, packed with shrapnel.

Dzhokhar Tsarnaev was injured in the gun battle with police and has been held in a prison hospital near Boston since his capture on April 19.

The brothers are from a family of ethnic Chechen Muslims from Russia and had been living in the US for about a decade.