The student was stabbed in the capital in April, and 11 people were killed in a market bombing in August.
"The cases have been united, as the same suspects appear in both of them," Simon Tsaturyan said.
Vagan Abramyants, a 17-year-old student at the Moscow Academy of Management, was attacked and stabbed to death on the platform of Pushkinskaya metro station in central Moscow, at about 5 p.m. on April 22.
On August 21 an explosion rocked the Cherkizovsky market in northeastern Moscow killing 11 and injuring at least 49 people.
On the day of the bombing, police arrested three students of Moscow institutes, Ilya Tikhomirov, Oleg Kostyrev and Valery Zhukovtsov. The police later arrested 25-year-old Nikolai Korolyov.
The bombing suspects confessed to being motivated by race-hate. As with most markets in Moscow, many traders at the Cherkizovsky market are from the North Caucasus region and former Central Asian Soviet republics, as well as China and Vietnam.
