Two huge explosions went off at around 2:30pm local time, severely damaging the four-story building where some 200 people work.
Chechen Interior Minister Ruslan Tsakayev told the Interfax news agency the bombers drove both a delivery truck and a sport utility-style vehicle used by the Russian military laden with explosives into the structure.
Neither the head of the Chechen administration, Akhmad Kadyrov, nor his deputy, Mikhail Babich, were in the building at the time of the attack, Russia’s NTV television reported.
Kadyrov, who was in Moscow, told Interfax that one of the trucks broke through three guard-post cordons surrounding the government headquarters.
“How could the terrorists have managed to break through three fences around the government building? The guards’ actions must be investigated,” Kadyrov said.
He said it was useless to beef up security — including normal traffic checks — after the attack.
“How many times have we conducted these traffic checks, and to what aim? Just as before, the terrorists act as if they were masters of Grozny,” he said.
Interfax quoted Aslan Magomadov, an envoy of President Vladimir Putin, as saying there would be “serious questions” for the Ministry of Justice, Federal Guards Service and the Federal Security Service.
Television pictures showed bodies scattered on the frozen ground as small groups of dazed and wounded staff and security personnel staggered towards medical crews. Footage broadcast by Russian television showed the building, one of the city’s most heavily guarded, completely gutted.
There were no immediate claims of responsibility for the bombing but authorities said it bore the hallmarks of an attack by guerrillas fighting for the withdrawal of Russian forces from Chechnya.
This bombing, which took place just two months after a mass hostage-taking by Chechen rebels in Moscow, is the latest in a series of attacks that have undercut Russian claims that the rebels have been largely defeated.
Russian forces have been fighting the separatist guerrillas on and off since 1994. An agreement in 1996 gave the province de facto independence. After a series of 1999 apartment bombings blamed on Chechen militants, Russian troops reoccupied the region and ousted the elected president, Aslan Maskhadov.
European powers have urged Putin to resume peace talks with Maskhadov, a call rejected by Russia. The Kremlin says Maskhadov is either complicit with the rebels behind the recent attacks or incapable of preventing them and thus irrelevant.
President Vladimir Putin plans a March referendum on a political settlement that would keep Chechnya within Russia.