Boston bomb suspect Tsarnaev pleads not guilty

The 19-year-old Tsarnaev, making his first court appearance, entered the federal courtroom in Boston in handcuffs, shackles and wearing an orange jumpsuit.

"Not guilty," the 19-year-old ethnic Chechen Muslim, a naturalized US citizen, said repeatedly as the 30 counts were read out at the arraignment, which lasted seven minutes.

The room was packed with emotional victims of the bombings at the Boston Marathon finish line, some of whom needed canes to walk.

Also in court were many journalists and a few people who identified themselves as friends of Tsarnaev, who is accused of carrying out the attacks, which left three people dead and more than 260 wounded.

Seventeen of the counts against him are punishable by the death penalty or life imprisonment.

The attacks stunned America with scenes of carnage and chaos at one of the country's premier sporting events. The bombs were packed with metal fragments to cause maximum damage, and several people lost one or more limbs.

Tsarnaev is accused of plotting and carrying out the attacks with his 26-year-old brother Tamerlan, who died in a shootout with police as the pair tried to escape the Boston area several days later.