Russian national colours are emblazoned on the façade of the Khalifa University in Abu Dhabi.

The UAE lit up its most prominent landmarks, most notably Burj Khalifa, the Abu Dhabi National Oil Company (ADNOC) building, the Burj Al Arab Hotel and the Dubai Frame on Saturday evening, in the colors of the Russian flag in solidarity with the victims of the terrorist attack.

Camouflage-clad gunmen opened fire with automatic weapons at concertgoers near Moscow on Friday, killing at least 133 people and injuring hundreds in an attack.

The UAE has expressed its strong condemnation of these criminal acts, and its permanent rejection of all forms of violence and terrorism that aim to destabilize security and stability and are inconsistent with international law.

Russia on Saturday said the four suspected gunmen arrested over Friday's attack on a Moscow concert hall were not Russian citizens.

"They are all foreign nationals," the interior ministry said in a statement, as Russian media reported some were nationals of Tajikistan, a country that borders Afghanistan and where the Daesh group is active.