Kremlin spokesman Dmitry Peskov has spoken with reporters this morning and he was asked about Friday's Moscow concert hall attack.
Russian president Vladimir Putin has tried to link the attack to Ukraine, saying that it was carried out by radical Islamists but they had attempted to escape to Ukraine afterwards.
The four main suspects are from Tajikistan.
Mr Peskov was asked about the alleged link with Ukraine and he said: "I have nothing to add to what has already been said on this topic."
He said the comments from Russian officials on the attack were base don "preliminary data" and that the head of Russia's investigative committee had reported to Putin on Monday.
Meanwhile, Nikolai Patrushev, secretary of Russia's Security Council and a close ally of Putin, was more open about his suspicions.
News outlet SHOT published a video of a brief exchange in which a reporter asked him: "ISIS or Ukraine?" as he walked past.
"Of course Ukraine," he replied.
The US has blamed ISIS-K, an Afghan branch of Islamic State, but Russian officials have not yet accepted this.
Some 139 people were killed in the attack.
