Two suspects in connection to the deadly Moscow concert hall terrorist attack appeared in the Basmanny District Court on Sunday night. The Associated Press reported that the court hearing was held under heavy police presence, with authorities expected to determine pretrial restrictions for the two men accused of opening fire on the attendees at Crocus City Hall.

The attack, which took place on Friday, claimed the lives of more than 130 people. Russian authorities made four arrests on Saturday, along with detaining seven additional individuals suspected of involvement in the assault.

The Islamic State promptly claimed responsibility for the attack, a claim which has been confirmed by U.S. authorities. Adrienne Watson, spokesperson for the National Security Council, stated that "ISIS bears sole responsibility for this attack. There was no Ukrainian involvement whatsoever." Watson also revealed through social media that the U.S. had previously warned Russia about a potential terrorist attack earlier in the month. The U.S. Embassy in Russia had issued a public advisory urging American citizens to avoid large gatherings, including concerts.

As the nation mourns the victims of the devastating attack, Sunday was observed as a national day of mourning in Russia. The toll from the incident stands at least 137 people dead, with another 154 reported injured.

The court proceedings will play a crucial role in determining the fate of the two suspects. As investigations continue, authorities will be seeking further information on the motive and potential accomplices involved in this tragic incident.