BOSTON (AFP) - A US jury on Monday returned the first conviction over the 2013 Boston Marathon attacks, finding a university friend of the prime suspect guilty of obstructing the investigation into the bombings.

Azamat Tazhayakov, 20, was found guilty of taking a backpack from alleged bomber Dzhokhar Tsarnaev's dorm room but not a laptop, which was tossed in a dumpster and took two days to recover.

He will be sentenced on October 16.

Legal experts said Tazhayakov, who is from Kazakhstan, would serve prison time in the United States and then be deported.

The seven men and five-women jury returned the verdict after a two-week trial in a federal court in Boston, the first trial connected to the April 15, 2013 attacks at the Boston marathon.

Three people were killed and 264 injured when two pressure-cooker bombs exploded at the race's finish line, in an attack allegedly carried out by Chechen brothers Dzhokhar and Tamerlan Tsarnaev.

Mr Dzhokhar Tsarnaev is due to stand trial in November - he is accused of 30 federal charges and could face the death penalty if convicted.

Police shot dead his older brother Tamerlan in the days after the attacks.