Russian President Vladimir Putin has suggested that Ukraine was linked to the attack on a concert hall on the outskirts of Moscow that killed 115 people.

The so-called Islamic State group’s (IS) Afghanistan branch claimed responsibility for Friday’s attack on the Crocus City Hall in a statement posted on social media.

A US intelligence official told the Associated Press that American agencies had confirmed that the group was responsible for the attack.

However, some Russian politicians pointed the finger at Ukraine shortly after the attack – accusations that Ukraine has strongly denied.

Mr Putin said all four people directly involved in the attack had been detained and suggested they were trying to cross the border into Ukraine while escaping.

He said additional security measures have been imposed throughout the country and declared that Sunday will be a nationwide day of mourning.

The attack was the deadliest in Russia in years and left the concert hall a smouldering ruin.

The venue had a capacity of more than 6,000 people in Krasnogorsk, on Moscow’s western edge.