Federal prosecutors have asked a judge to reject a bid by Boston Marathon bombing suspect Dzhokhar Tsarnaev to dismiss charges against him over concerns about an under representation of African-Americans and people over 70 on federal juries in Massachusetts.

Tsarnaev's lawyers said their review of the makeup of grand juries and trial juries in Massachusetts last month revealed ``substantial violations'' of the federal jury selection law and a constitutional requirement that juries represent a fair cross-section of the population.

In a response filed in U.S. District Court on Friday, prosecutors said Tsarnaev has not shown a failure to comply with the law or an unconstitutional disproportionality.

Tsarnaev is awaiting trial on 30 charges. Two bombs placed near the finish line of the 2013 marathon killed three people and injured more than 260.