Russia, Sep 1 (BNO NEWS): Two explosions and a shooting in Russia's turbulent North Caucasus region on Thursday left four people killed and five others injured as security forces launched a manhunt for insurgents, officials said.

Lieutenant Colonel Ibragim Dzhabrailov, a senior officer of the Federal Security Services (FSB), was killed on Thursday morning in a car bombing on a highway in the city of Khasavyurt, located in Russia's North Caucasus republic of Dagestan.

"An improvised explosive device of an unknown type detonated when an off-road vehicle of the FSB department senior officer was passing by," a source in the investigation department of Dagestan said, as quoted by the Ria Novosti news agency.

The FSB officer was traveling with four of his relatives who were hospitalized with injuries of varying degrees, the source reported.

Also in Russia's North Caucasus, local police chief Colonel Muayed Sizhazhov was found dead in a parked police car in the town of Baksan, in the mountainous district of Kabardino-Balkaria, German Press Agency DPA said.

Sizhazhov, who had been an area security forces commander and headed investigations into suspected insurgents, died from multiple gunshot wounds, DPA reported.

Earlier on Thursday, two men were killed and one was injured when a blast hit a private house in the Pliyevo village in Nazran, the capital of Ingushetia republic. The accident could have been caused by the detonation of an explosive device, according to police.

The four deaths came one day after three suicide bombers killed nine and injured 20 in the Leninsky district of Grozny, the capital city of Russia's Chechen Republic. Among the fatal victims were seven police officers.

After the attack, Russian authorities deployed police and army officers in Grozny and other Caucasus cities, as children throughout the region began the school year. Security also was tight in the region of North Ossetia-Alania, where memorial services were held to honor the hundreds of people who died in September 2004 during a three-day hostage crisis at a school in Beslan.

Russia has been battling Islamist insurgency in the North Caucasus, which saw two violent wars against separatists in Chechnya during the past 20 years. Ingushetia, along with the neighboring republic of Dagestan, has been experiencing increased violence from both street brawls and terrorism in the recent years.