A Moscow court has ordered the detention of four suspects arrested in connection with a terrorist attack that claimed at least 137 lives at a concert hall in the Russian capital on March 22.

The court ordered that the men, all of whom are citizens of Tajikistan, be held in pre-trial custody until May 22. The suspects are identified as Dalerdzhon Mirzoyev, 32, Saidakrami Rachabalizoda, 30, Shamsidin Fariduni, 25, and Mukhammadsobir Faizov, 19.