With dozens injured and dozens more feared buried under the rubble of the damaged building, local officials warned the death toll may continue to rise.

Russian and Chechen officials immediately condemned the apparent suicide attack on the building in Znamenskoye, 15 kilometers north of the Chechen capital Grozny, as an attempt to derail the fragile peace process in the breakaway republic.

The death toll stood at 40 by midday Monday, with around 100 injured, the Chechen prosecutor's office said, quoted by RIA Novosti news agency.

It said the truck had been packed with one ton of explosives.

Police and interior ministry soldiers sealed off the site as workers with the republic's emergencies ministry and federal troops searched for victims in the rubble of the building, which housed the local administration, police and FSB security services.

Security guards shot at the truck as it came crashing through the gates surrounding the government complex just after the start of the workday Monday morning, according to Sultan Akhmetkhanov, head of the republic's Nadterechny district.

"Security services opened fire on the truck but unfortunately could not stop it,'' he told ITAR-TASS news agency.

The blast damaged six other buildings, Interfax news agency said.

Separatist rebels have vowed to step up attacks to disrupt the results of a controversial March 23 referendum that sealed Chechnya's place in the Russian Federation.

Violence has flared since the poll, when voters massively approved a new pro-Moscow constitution following several months of relative calm.

Last month, 16 people were killed in a minibus blast claimed by separatist rebels.

In the last major rebel attack on December 27, some 80 people were killed when rebels drove two explosives-packed vehicles into headquarters of Chechnya's pro-Russian administration in Grozny.

President Vladimir Putin, who sent federal troops into Chechnya to quell the separatist insurgency while prime minister in October 1999, accused the attackers of aiming to disrupt the Moscow-backed peace process.

"These actions are aimed at stopping the process of a political solution in Chechnya,'' Putin said, quoted by Interfax. "We cannot and will not allow this to happen.''

Observers had warned that Moscow was carrying out the vote before security had been established in the war-torn republic and many urged Putin to first open peace talks with the separatists.

"This explosion shows that the idea of the referendum led to nothing,'' said independent defence analyst Pavel Felgenhauer.

"The separatists are turning more and more to terrorist tactics and are supported by the population -- if this were not the case, their resistance would not be able to continue.''

(China Daily May 13, 2003)