A powerful explosion has killed 30 people at a government compound in Russia's breakaway Chechnya region.

The blast, caused by a truck packed with explosives, left an enormous crater and severely damaged the local administration building in a town of Znamenskoye, north of the region's capital, Grozny.

The headquarters of the internal security police was also targeted.

Dozens of injured were taken to a hospital after the explosion.

The head of Chechnya's pro-Russian administration, Akhmad Kadyrov, said the incident again shows that Russian and Chechen security services are unable to prevent attacks by separatist fighters, who have been at war with Russia for most of the past eight years.

In December, a truck bomb attack on the headquarters of the pro-Moscow government in Grozny killed about 80 people and destroyed the main government compound in the city.

That truck managed to pass through several checkpoints and penetrate into the heart of the city's administrative district, raising serious questions about security procedures.

President Vladimir Putin insists that the long-running war in Chechnya is all but over, saying a referendum held in March proved that most Chechens want to remain part of Russia.

But separatist groups mount almost daily hit-and-run attacks against Russian troops and local authorities.

The rebels direct most of their actions at highway checkpoints in Chechnya.

Russian troops fought an inconclusive war in the region in the mid-1990s before withdrawing in 1996.

President Putin ordered troops back into Chechnya in 1999, and his widespread popularity is believed to be due in large part to his tough line on the issue of independence.