Accused Boston Marathon bomber Dzhokhar Tsarnaev pleads not guilty to charges relating to the deaths of four people in April.

He has been charged with 30 federal charges, including using a weapon of mass destruction to kill.the bombings that killed three people and wounded more than 260

The 19-year-old ethnic Chechen was charged late last month with setting off home-made pressure-cooker bombs, assembled by him and his older brother, in a crowd of thousands of race spectators on 15 April.

He was also charged with the murder of a university police officer.

Mr Tsarnaev appeared in court with a swollen face and his arm in a cast.

He smiled when his sisters arrived in court.

Mr Tsarnaev leaned toward a microphone and said, "Not guilty" in a Russian accent to 30 federal charges, including using a weapon of mass destruction to kill.

He made a kissing motion toward his family as he was led out of the courtroom.

A shooting, and a later gun battle with police in the suburb of Watertown, Massachusetts, led to the death of 26-year-old Tamerlan Tsarnaev.

Following a day-long lockdown of most of the Boston area as police searched for Dzhokhar, the teenager was found badly wounded, hiding in a boat in a backyard.

The marathon attack injured about 264 people, with many losing legs.

Mr Tsarnaev's attorney, public defender Miriam Conrad, faces the challenge of sparing him the death penalty.

According to court papers, Mr Tsarnaev scrawled a note on an inside wall and beams of the boat in which he hid.

"The US Government is killing our innocent civilians," the note read, according to court papers. "We Muslims are one body, you hurt one you hurt us all.

"Now I don't like killing innocent people it is forbidden in Islam but due to said it is allowed. Stop killing our innocent people and we will stop."

Mr Tsarnaev was badly wounded during the gun battle and arrest.

After initially being confined at a city hospital, he was moved to a prison west of Boston.

Prosecutors have declined to comment on his current condition or if he is still being held at the Fort Devens, Massachusetts, facility.

Krystle Campbell, 29, Lingzi Lu, 23, and eight-year-old Martin Richard died in the bombing.

Three days later, the Tsarnaevs shot dead Massachusetts Institute of Technology police officer Sean Collier, according to the indictment.