Russia on Saturday said it had arrested 11 people – including four gunmen – over the attack on a Moscow concert hall claimed by the Islamic State, as the death toll rose to 115. Moscow appears to have ruled out the possibility of Islamic State's involvement, after the group claimed responsibility, and is now seeking a Ukrainian link to the attacks. Ukraine has vehemently denied playing a role.

In a televised address on Saturday, Russian President Vladimir Putin said all four gunmen had been arrested before they had a chance to cross the border into Ukraine.

"I am speaking to you today in connection with the bloody, barbaric terrorist act, the victims of which were dozens of innocent, peaceful people," Putin said in his first public remarks since the attack.

"All four perpetrators of the terrorist attack who shot and killed people have been detained. They were travelling towards Ukraine where, according to preliminary information, they had a window to cross the border," the Kremlin leader said.

Russia's FSB security service said earlier the assailants had been "in contact" with people in Ukraine as they tried to flee the country.

Camouflaged gunmen opened fire at the packed Crocus City Hall in Moscow's northern suburb of Krasnogorsk on Friday evening ahead of a concert by Soviet-era rock band Piknik in the deadliest attack in Russia for at least a decade. Authorities have warned the number of fatalities was set to keep rising, with more than 100 still hospitalised and a search of the burnt-out venue ongoing.

Before Putin's public address, some Russian lawmakers had pointed to Kyiv, without providing evidence.

Ukraine, which has been facing a Russian military offensive for the past two years, had "nothing to do" with the attack, according to a statement by presidential aide Mykhailo Podolyak on Telegram.

At least 115 killed

Russia's Investigative Committee, which probes major crimes, said rescue workers were still working on site, pulling bodies from the building.

"The emergency services have found more bodies while removing the rubble. The death toll now stands at 115 people," it said in a statement on Telegram.

The number of fatalities was likely to rise further, as the governor of the Moscow region said rescuers would continue to scour the site for "several days."

Investigators said people died both from gunshot wounds and from smoke inhalation after a fire engulfed the 6,000-seater venue.

"The terrorists used a flammable liquid to set fire to the concert hall's premises, where spectators were located, including wounded," the Investigative Committee said.

Flames had quickly spread through the venue on Friday after reports of the mass shooting, with screaming concert-goers rushing to emergency exits.

Some filmed the gunmen from the upper floors as they appeared to methodically walk through the stalls shooting people, footage shared on social media showed.

The Islamic State group claimed responsibility on Friday, saying its fighters attacked "a large gathering" on Moscow's outskirts and "retreated to their bases safely".

Global condemnation

Russian authorities have called it a "terrorist attack," but have not commented on the Islamic State's claim.

Some 107 people were still in hospital on Saturday morning, according to Russia's Emergency Situations Ministry.

Russian Telegram channels, including Baza which is close to the security services, and a lawmaker said some of the suspects were from the central Asian nation of Tajikistan.

In a statement, Tajikistan's foreign affairs ministry said it had not received any information from Moscow about the involvement of its citizens.

In Moscow, residents formed long queues in the Saturday morning rain to donate blood, according to videos posted by state media outlets.

Memorial posters featuring a single candle replaced advertising billboards at some Moscow bus stops, the RIA Novosti state agency reported.

Major events were cancelled across the country, including a friendly football match between Russia and Paraguay set to take place in Moscow on Monday.

Statements of condemnation from world leaders continued to roll in.

On Saturday, a spokesperson for Afghanistan's foreign ministry said the Taliban "condemns in the strongest terms the recent terrorist attack in Moscow, Russia ... and considers it a blatant violation of all human standards."

US warning dismissed

Attention is also being focused on Russia's powerful intelligence services in the wake of the attack.

Just three days before, Putin had publicly dismissed Western warnings of an imminent attack in Moscow as propaganda designed to scare Russian citizens.

On 7 March, the US embassy in Russia had issued a security alert saying it was "monitoring reports that extremists have imminent plans to target large gatherings in Moscow, to include concerts."

Washington said it had directly warned Russian authorities about a "planned terrorist attack" possibly targeting "large gatherings" in Moscow.

The United States had "shared this information with Russian authorities," National Security Council spokeswoman Adrienne Watson said.

But speaking to FSB chiefs last Tuesday, Putin said: "Recent provocative statements by a number of official Westerns structures about the possibility of terrorist attacks in Russia ... resembles outright blackmail and an intention to intimidate and destabilise our society."

Earlier in March, the FSB said it had killed Islamic State militants who were planning an attack on a Moscow synagogue.

Over recent weeks the agency has announced on an almost daily basis the arrest of several pro-Ukrainian saboteurs it said were plotting attacks on Russian military infrastructure.