Boston Marathon bombing suspect Chechen Dzhokhar Tsarnaev has pleaded not guilty to 30 charges including the use of a weapon of mass destruction.

Dzhokhar Tsarnaev, 19, entered his plea during his first public appearance in court Wednesday. More than half of the charges lobbed against him potentially imply the death penalty.

His arm in a cast, Tsarnaev made his first courtroom appearance since his capture at the end of a chaotic week in April.

Wearing a bright orange overall he walked calmly into court 10 at the Federal Court in Boston.

He fidgeted in his seat and was then told to stand as the different charges were read to him.

The 19-year-old smiled crookedly – he appeared to have a jaw injury – at his sisters.

Tsarnaev leaned over a microphone and said, “Not guilty” over and over in a Russian accent, before being led out of the courtroom.

He made a kissing motion toward his family as he left.

The proceedings lasted just seven minutes and took place in a courtroom packed with victims of the bombing, their families, police officers, and members of the public and the media.

The April 15 attack killed three people and wounded more than 260 others.

Authorities say Tsarnaev orchestrated the attack along with his older brother, Tamerlan Tsarnaev, who died following a shoot-out with police three days after the bombing.

Dzhokhar Tsarnaev was arrested on April 19 when he was found hiding in a boat in a suburban backyard.

He was initially charged in hospital, where he was recovering from wounds suffered in another police gunfight.

Reporters and spectators began lining up for seats in the Boston courtroom at 7.30am as a dozen Federal Protective Service officers and bomb-sniffing dogs surrounded the building.

Four hours before the hearing, the defendant arrived at court in a four-vehicle convoy that included a van, a Humvee and a state police car.

A group of about a dozen Tsarnaev supporters cheered as the cars arrived.

The demonstrators yelled, “Justice for Jahar!” as Tsarnaev is known. One woman held a sign that said, “Free Jahar.”

Lacey Buckley, 23, said she travelled from her home in Washington state to attend the arraignment.

Ms Buckley said she has never met Tsarnaev but came because she believes he is innocent.

“I just think so many of his rights were violated. They almost murdered an unarmed kid in a boat,” she said.

A group of friends who were on the high school wrestling team with Tsarnaev at Cambridge Rindge and Latin waited in line outside the courtroom for hours, hoping to get a seat.

One ex-teammate, Shun Tsou, 20, of Cambridge, called Tsarnaev “a silent warrior type”.

“There was nothing sketchy about him,” said Mr Tsou, adding that he had not formed an opinion on Tsarnaev’s guilt or innocence.

Prosecutors say Tsarnaev, a Muslim, wrote about his motivations for the bombing on the inside walls and beams of the boat where he was captured.

He wrote the US government was “killing our innocent civilians”.

“I don’t like killing innocent people,” he said, but also wrote: “I can’t stand to see such evil go unpunished. … We Muslims are one body, you hurt one you hurt us all.”

Three people – Martin Richard, aged eight; Krystle Marie Campbell, 29; and Lingzi Lu, 23 – were killed by the bombs, which were improvised from pressure cookers.

Authorities say the Tsarnaevs also killed Massachusetts Institute of Technology officer Sean Collier days later while they were on the run.

Numerous bombing victims had legs amputated after the two explosions, which detonated along the final stretch of the race a couple hours after the elite runners had finished.

Following the appearance Tsarnaev was driven back to the secure hospital in Massachusetts where he is being held – his case will be heard in court again in September.

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