Russia said on Saturday it had arrested all four gunmen suspected of carrying out a shooting massacre in a concert hall near Moscow, and President Vladimir Putin pledged to track down and punish those behind the attack.
Militant Islamist group Islamic State claimed responsibility for Friday's rampage, but there were indications that Russia was pursuing a Ukrainian link, despite emphatic denials from Ukrainian officials that Kyiv had anything to do with it.
Moscow regional Governor Andrei Vorobyov said 133 bodies had been recovered from the rubble in 24 hours and doctors were "fighting for the lives of 107 people". State TV editor Margarita Simonyan, without citing a source, had earlier given a toll of 143.
In a televised address, Putin said 11 people had been detained, including the four gunmen. "They tried to hide and moved towards Ukraine, where, according to preliminary data, a window was prepared for them on the Ukrainian side to cross the state border," he said.
Russia's FSB security service said the gunmen had contacts in Ukraine and were captured near the border. It said they were being transferred to Moscow.
Neither Putin nor the FSB publicly presented any proof of a link with Ukraine, with which Russia has been waging war since Moscow invaded 25 months ago. Ukrainian President Volodymyr Zelenskiy said it was typical of Putin and "other thugs" to seek to divert blame.
Ukrainian military intelligence spokesperson Andriy Yusov told Reuters: "Ukraine was of course not involved in this terror attack. Ukraine is defending its sovereignty from Russian invaders, liberating its own territory and is fighting with the occupiers' army and military targets, not civilians."
Islamic State has a strong motivation to strike Russia, which intervened against it in Syria's civil war in 2015, and security analysts said the IS claim seemed plausible as it fit the pattern of past attacks.
Putin cast the enemy as "international terrorism" and said he was ready to work with any state that wanted to defeat it.
"All the perpetrators, organizers, and those who ordered this crime will be justly and inevitably punished. Whoever they are, whoever is guiding them," Putin said. "We will identify and punish everyone who stands behind the terrorists, who prepared this atrocity, this strike against Russia, against our people."
A senior Russian lawmaker, Andrei Kartapolov, said that if Ukraine was involved, then Russia must deliver a "worthy, clear and concrete" reply on the battlefield.
Western nations, including the United States, whose ties with Moscow have been fraught since its invasion of Ukraine, condemned the attack and expressed sympathy for the Russian people affected. Arab powers and many former Soviet republics also expressed shock and sent their condolences.
The White House said the US government shared information with Russia early this month about a planned attack in Moscow and issued a public advisory to Americans in Russia on March 7. It said Islamic State bore sole responsibility for the attack.
"There was no Ukrainian involvement whatsoever," US National Security Council spokesperson Adrienne Watson said on Saturday.
But Russia's ambassador to the United States, Anatoly Antonov, said early on Sunday the US had not shared any specific information with the embassy before the shooting.
"No specific information, nothing was given to us," Antonov said, according to Russia's TASS state news agency. He said there has also been no contact after the attack.
Verified footage showed camouflage-clad gunmen opening fire with automatic weapons in the Crocus City Hall near Moscow. Video showed people taking their seats, then rushing for the exits as repeated gunfire echoed above screams.
Investigators said some died from gunshot wounds and others in a huge fire that broke out in the complex. Reports said the gunmen lit the blaze using petrol from canisters they carried in rucksacks.
People fled in panic. Baza, a news outlet with good contacts in Russian security and law enforcement, said 28 bodies were found in a toilet and 14 on a staircase. "Many mothers were found embracing their children," it said.
Russian lawmaker Alexander Khinshtein said the attackers fled in a Renault vehicle that was spotted by police in Bryansk region, about 340 km (210 miles) southwest of Moscow on Friday night. He said a car chase ensued after they disobeyed orders to stop.
Khinshtein said a pistol, a magazine for an assault rifle, and passports from Tajikistan were found in the car. Tajikistan is a mainly Muslim Central Asian state that used to be part of the Soviet Union.
BBC News' Russian Service quoted an unnamed source familiar with the security response as saying one attacker was killed in the concert hall and another in the car in Bryansk. The BBC said it had a copy of that dead man's passport, who it said was a 30-year-old citizen of Tajikistan.
TV editor Simonyan published a video showing one of the suspects, a young, bearded man, being interrogated aggressively by a roadside, replying in heavily accented Russian to a series of barked questions. He said he had flown from Turkey on March 4 and had received instructions from unknown people via Telegram to carry out the attack in exchange for money.
The man was trembling throughout the questioning. He was initially shown lying on his stomach with his hands bound behind his back, his chin resting on the boot of a figure in a camouflage uniform. Later, he was hauled up onto his knees.
Another man with cuts and bruises to his face was shown being questioned via an interpreter while sitting on a bench with bound hands and feet.
The Kremlin said Putin had held conversations with the leaders of Belarus, Uzbekistan, and Kazakhstan, and all sides affirmed their willingness to work together to fight terrorism.
Reuters