'Radical Islamists' behind Moscow attack, admits Putin

However, he suggested that Ukraine was also somehow involved.

Russian President Vladimir Putin acknowledged for the first time that 'radical Islamists' were responsible for last week's attack on a concert hall outside Moscow.

However, he suggested that Ukraine was also somehow involved, Al Jazeera reported.

Russian authorities have detained 11 people in connection with the March 22 attack on Crocus City Hall.

In a televised meeting on Monday, Putin said, "We know that the crime was committed by the hands of radical Islamists, whose ideology the Islamic world itself has been fighting for centuries."

"This atrocity may be just a link in a whole series of attempts by those who have been at war with our country since 2014 with the hands of the neo-Nazi Kyiv regime," he said, referring to Ukraine, according to Al Jazeera report.

Putin stressed that it was necessary to respond to that question.

He asked, "Of course, it is necessary to answer the question, 'Why after committing the crime the terrorists tried to go to Ukraine?' Who was waiting for them there?"

Putin said the planned terrorist attack hoped to sow panic but it was met with unity and resolve to counter this evil, according to the transcript released on the Kremlin website.

He did not mention ISIS which claimed responsibility for the Moscow attack.

He said, "We know whose hands were used to commit this atrocity against Russia and its people. We want to know who ordered it."

Since Friday, the Islamic State in Khorasan Province has said several times that it was behind the attack, and ISIL-affiliated media channels have released graphic videos of the gunmen during the attack.

After ISIS claimed responsibility for the attack, United States intelligence has backed up its claims.

On Monday, Kremlin spokesperson Dmitry Peskov refused to assign blame and asked reporters to wait for the results of the probe in Russia, Al Jazeera reported.

He even refused to comment on reports that the US warned authorities in Moscow on March 7 about a possible attack and said that any such intelligence is confidential.

On Sunday, a Moscow court charged four men with carrying out a 'terrorist' attack. At their court appearance, the gunmen showed signs of being severely beaten.

The four suspects, named by Russian authorities as Dalerdzhon Mirzoyev, Saidakrami Rachabalizodu, Shamsidin Fariduni and Muhammadsobir Fayzov were tried in Basmanny Court in Moscow.

All four are to be held in detention until at least May 22, the court said.

One of the men charged with committing the terror attack is a Tajik national, TASS reported.

All four are from Tajikistan and have been in Russia on either temporary or expired visas, CNN reported.

Russian Prime Minister Mikhail Mishustin said the investigation is being conducted. However, he promised that 'the perpetrators will be punished. They do not deserve mercy'.

Former Russian President Dmitry Medvedev, who now serves as deputy head of Russia's Security Council, asked authorities to 'kill them all'.

According to the Russian Investigative Committee, a total of 137 people died in the March 22 terror attack at the Crocus City Hall music venue and the death toll is likely to go up further.

The Moscow Region health ministry reported 182 people injured.

A total of 11 people involved in the attack were apprehended, including four suspected attackers, who sought to flee towards the Ukrainian border, TASS reported.

During his televised address, Russian President Vladimir Putin said that Ukraine prepared a 'window' for the attackers to cross the border and vowed to identify and punish everyone behind the attack. He also declared March 24 a national mourning day.

Putin had said, "We will investigate this terrorist attack and we already have some results. All the four perpetrators, who were directly involved who were gunning people down, killing people."

"They were found and apprehended. They tried to escape. They were moving towards the border with Ukraine and we have data that suggests that they were about to be moved towards the territory of Ukraine by those in Ukraine," he added.

The concert venue, with an estimated capacity of 7,500, was almost full when the terrorists struck and the assault took place ahead of a performance by the Russian rock band Picnic, RT news agency reported earlier.

According to the mobile phone footage and eyewitness accounts, at least five gunmen wearing military-style gear and carrying assault rifles first opened fire at unarmed security guards at the main entrance to the venue.

They then proceeded to shoot indiscriminately at the fleeing crowd of panicked visitors.

Once the terrorists reached the concert hall, they appeared to set fire to rows of chairs inside, with the blaze quickly engulfing much of the building, including its roof.

According to a CNN report, the US warned Moscow that ISIS terrorists were determined to target Russia in the days before assailants stormed Crocus City Hall in an attack that killed scores of people, but Vladimir Putin rejected the advice, calling it 'provocative'.

US National Security Council spokesperson Adrienne Watson said the US government had 'shared this information with Russian authorities in accordance with its longstanding 'duty to warn' policy'.