BOSTON -- Two college friends of the surviving Boston Marathon bombing suspect pleaded not guilty Tuesday to allegations they conspired to obstruct justice by agreeing to destroy and conceal some of their friend's belongings as he evaded authorities.

Wearing shackles and orange jail jumpsuits, both 19-year-old defendants looked happy to see family across the courtroom before emphatically entering their pleas.

Dias Kadyrbayev and Azamat Tazhayakov, both Kazakhstan nationals who shared an apartment in New Bedford, Massachusetts, became friends with bombing suspect Dzhokhar Tsarnaev when they all started school at the University of Massachusetts-Dartmouth in 2011.

Dzhokhar Tsarnaev is accused of setting off two bombs near the race's finish line that killed three and wounded hundreds April 15. He has pleaded not guilty. Authorities say he was working with his older brother Tamerlan, who died during the manhunt for the suspects days later.

On April 18, Tsarnaev's friends took his laptop from his dorm room, along with a backpack that had fireworks with explosive powder and a jar of petroleum jelly, federal authorities alleged in an indictment last week.

They say Kadyrbayev had gotten a text from Tsarnaev suggesting that he could go to his dorm room and "take what's there." The indictment also alleged that Kadyrbayev later put the backpack with the fireworks and jelly in a trash bin outside the New Bedford apartment after Tazhayakov agreed.

It also said Kadyrbayev told Tazhayakov he believed Tsarnaev had used the jelly "to make bombs."

Kadyrbayev's attorney Robert Stahl has said his client never knowingly took evidence from the dorm room and co-operated with the FBI.

Tazhayakov's lawyer Arkady Bukh has said his client never agreed to anything when it came to disposal of the backpack with the fireworks.

Both defendants face up to 25 years in prison.

Tazhayakov's father said afterward that his son is "absolutely not guilty" and that the FBI made a mistake by arresting him.

Kadyrbayev's father, Murat Kadyrbayev, said through a Russian-speaking member of the Boston media that he feels badly for everyone who suffered during the bombing and he prays for their souls, along with his son because he's sure he's innocent.

Also Tuesday, lawyers for the father of a Chechen man who was fatally shot during questioning about ties to Tamerlan said he would have had trouble attacking officers because he was recovering from a knee injury.

Ibragim Todashev, 27, was killed in May while FBI agents and police questioned him at his Florida apartment. Officials originally said Todashev lunged at an agent with a knife. But they later said it was no longer clear what happened. An investigation is being led by the FBI.

At a news conference, the lawyers said that a former detective they hired to investigate the death told them that all the agents in the room would have drawn their weapons and fired if they believed their lives were in danger -- but based on their findings, they don't believe that happened.

Todashev's father, Abdulbaki Todashev, also spoke at the news conference. Todashev said he came to Florida from Chechnya last week to try to learn more about what happened. He brought to the news conference two posters with photos of his son, including a picture that showed Ibragim Todashev's stitched-up knee after surgery. The lawyers said the surgery was recent and that he was still limping at the time of questioning.

"My son was a very good boy," Abdulbaki Todashev said through a Russian translator. "He was a good grandson to his grandparents. He was a good brother. He was a good neighbour.

"He was innocent, and he was simply killed."