By Guy Faulconbridge
MOSCOW (Reuters) - The Kremlin said on Monday that no country was immune to terrorism when asked if there had been a major failure by security services in preventing Friday's deadly attack on a concert hall, the worst attack inside Russia for two decades.
At least 137 people were killed and 182 injured when four men burst into the Crocus City Hall, spraying people with bullets before setting fire to the 6,200-seat hall.
President Vladimir Putin said in an address to the nation on Saturday that all those responsible would be punished. He said 11 people had been detained, four heading towards Ukraine.
Kremlin spokesman Dmitry Peskov said on Monday it was inappropriate to comment on a claim of responsibility for the attack by Islamic State while the investigation was live.
"The investigation is underway," Peskov told reporters. "So far, no versions have been put forward at all."
When asked if such a deadly attack unfolding just outside the Russian capital was a failure for the special services, Peskov said emotions were running high but that no country was immune.
"Unfortunately, our world shows that no city, no country can be completely immune from the threat of terrorism," Peskov said. He said the special services worked tirelessly to defend Russia.
"The fight against terrorism is an ongoing process that requires full-scale international cooperation. But you can see that now in this most acute confrontational period, such cooperation is not being fully carried out in any way."
The Federal Security Service (FSB), the main successor the Soviet-era KGB, is one of Russia's most powerful institutions. It has been headed by Alexander Bortnikov since 2008, who briefed Putin on the course of the investigation after the attack.
U.S. INTELLIGENCE
The United States said it had warned Russia two weeks before about the possibility of an attack in Moscow. That intelligence prompted the U.S. embassy in Moscow to issue a warning that "extremists" had imminent plans for an attack.
Asked if Russian security services needed assistance from the West, Peskov said: "Our special services are working independently, now there is no question of any help."
Peskov declined to comment on intelligence details.
He said, though, that in conversations with other leaders since the attack, other heads of state had suggested improving international efforts to counter terrorism.
Some of the suspects were shown being interrogated in unverified footage published by Russian media and Telegram channels with close ties to the Kremlin.
One of the suspects was shown having part of his ear cut off and stuffed into his mouth. Another was shown with his hands tied and his hair held by an interrogator, a black boot beneath his head. Another was questioned in a hospital bed.
When they appeared in court on Sunday night, one had a bandage over his ear, another had a bruised face and another was shown in hospital robes.
"I leave this question without answer," Peskov said when asked about possible abuse of the suspects.