About 130 people were injured, dozens critically, when onstage fireworks set the ceiling of the Lame Horse nightclub ablaze soon after midnight, witnesses and officials said. Many victims were trapped in a panicked crush for the exit as they attempted to escape the flames and thick black smoke.

Authorities quickly arrested two registered co-owners of the club, its managing director, and two other suspects. One other suspect was injured in the fire and remains in critical condition.

Officials said club managers had ignored repeated demands from authorities to change the interior to comply with fire safety standards. Emergency Situations Minister Sergei Shoigu told Medvedev by videoconference from Perm that the club managers violated the law by running the fireworks display that triggered the fire.

The state-run railway company said the derailment late Friday could have been the result of sabotage, raising fears that the luxury train, popular with business executives and government officials, was the target of a terrorist attack.

The last three cars of the 14-car Nevsky Express left the tracks in the Tver province northwest of Moscow, the Emergency Situations Ministry said. Minister Sergei Shoigu said Saturday morning that 39 people were dead and 18 missing.

Health Minister Tatyana Golikova told reporters at the scene that 95 people were being treated in hospitals in the Tver and Novgorod region.

State-run Vesti-24 television showed grainy footage hours after the derailment of a dented passenger car flipped on its side, laying across the tracks.

A Vesti-24 reporter called the wreck a “terrible catastrophe,” saying he was looking at a “warped” carriage and could see other damaged cars as ambulances drove in and out of the cordoned-off site.

A shell “self-detonated” as ammunition was being loaded onto a truck at Russian Navy Arsenal No. 31 in Ulyanovsk, city about 900 kilometers (560 miles) east of Moscow, the ministry said on its Web site.

Ammunition in the truck exploded, killing the eight technicians and wounding two others.

The November 13 fire at the arsenal created a series of explosions resembling fireworks that went off about every 30 seconds, according to Russian media.

Two people were killed in that fire, the Defense Ministry said at the time.

The governor of the Ulyanovsk region, Sergey Morozov, said in an interview with Russian Channel One TV that the depot had “several thousand rail cars” of munitions.

The attacks, which killed at least four police officers and one civilian, came on the same day as a Chechen rebel group claimed responsibility for a Siberian industrial accident earlier this week and promised a new wave of terror across Russia.

Alexander Lukashenko, the President of Belarus, snubbed a meeting of former Soviet republics in Moscow yesterday in protest at a Russian ban on imports of 1,300 dairy products that earn his regime almost $1 billion a year.

President Medvedev of Russia rebuked his counterpart as not “a true partner” and told journalists that Mr Lukashenko had not even telephoned him to say that he was boycotting the summit of the Collective Security Treaty Organisation (CSTO). The body represents Russia, Belarus, Armenia, Kazakhstan, Uzbekistan, Tajikistan and Kyrgyzstan.

Mr Medvedev urged Belarus to end “hysteria” over the milk ban. But the split deepened when Belarus declared that a decision by the CSTO to establish a military rapid-reaction force was “illegitimate” because it had not been present at the summit.

Mr Medvedev was speaking at the end of a Russia-EU summit held against a background of deep divisions over security, trade and energy supplies.

He also signalled a new gas crisis may lie ahead, suggesting Ukraine lacks the money to pay for gas Russia provides.