At least three people were killed and nearly 50 injured on Monday in twin car blasts outside a court building in a southern Russian city in the restive region of Dagestan.
The local investigative committee initially said that "within the space of a few minutes, two cars blew up. At least eight people died."
The local interior ministry later revised the toll to three people killed and 44 injured -- most of them seriously.
The incident occurred only hours before federal security agencies announced they had prevented a terror attack on the capital by killing two Russian suspects in the Moscow region and arresting another who had allegedly received training on Afghanistan's border with Pakistan.
The Kremlin said Russian President Vladimir Putin had been personally informed about the foiled plot and the special security operation to capture the suspects.
The last major attack in Moscow in 2011 saw 37 people killed in a suicide bombing in Domodedovo international airport. A double suicide bombing in the Moscow metro in 2010 killed 40.
But attacks in Dagestan are almost a daily occurrence and range from shootings at police to larger bombings.
Witnesses in the southern city of Makhachkala said they saw at least two dozen cars damaged in the parking lot outside a bailiff's office after two bombs went off within 15 minutes of each other.
The force of the explosions sent metal shrapnel flying some 150 metres (500 feet) and tore metal electric wires hanging overhead to shreds.
Pools of blood could be seen outside the building on the scenic shore of the Caspian Sea.
Dagestan's police department said the second bomb went off after law enforcement officials arrived on the scene to investigate the first explosion.
ITAR-TASS quoted one police source as saying that the incident may have been an assassination attempt against a senior bailiff's office representative.
Reports said that two law enforcement officials and a bailiff's office employee had died.
Another investigator said the bombs might have been remotely set off. The police closed off traffic across a large section of the city of more than half a million people in a hunt for those responsible.
There were no immediate claims of responsibility from any of the guerrilla movements in the impoverished North Caucasus region.
Dagestan is one of Russia's most violent regions. It is also home to the parents of the Boston bombing suspects Dzhokhar and Tamerlan Tsarnaev.
The predominantly Muslim republic suffers from well-organised crime syndicates as well as an influx of armed guerrillas from the neighbouring republic of Chechnya.
War-wrecked Chechnya fought two brutal post-Soviet campaigns against federal troops and has now been placed under Moscow's control with the help of iron-fisted ruler Ramzan Kadyrov.
But Moscow has struggled to exert its influence on Dagestan and analysts believe that its local leadership remains weak.
"In essence, we are seeing a civil war (in Dagestan) between local underground forces and the law enforcement authorities," said independent security analyst Pavel Felgenhauer.
"Interior ministry generals believe this underground enjoys broad support from a section of the population," he said.
"This is a response to tough local law enforcement measures and to overall corruption."