A homicide car bomber attacked a group of police and soldiers in Russia's restive North Caucasus Thursday, wounding at least 23 people, while two security officers were killed in a drive-by shooting, officials said.

The bomber struck the group at a checkpoint in the city of Nazran in the province of Ingushetia, said Madina Khadziyeva, a spokeswoman for the Russian Interior Ministry's branch there. Ingushetia neighbors Chechnya to the west.

The explosion wounded 10 Interior Ministry troops, three local police officers and 10 civilians, many of whom were in critical condition, said Svetlana Gorbakova of Russia's top investigative body. She said three of the 10 civilians were children.

In a separate incident in Nazran later Thursday, two security officers were shot dead in their car by unidentified assailants in the drive-by shooting, Gorbakova said. Two colleagues were wounded in the attack, and the assailants escaped, she said.

There have been a series of suicide attacks in the region and other violence stemming from two separatist wars in Chechnya over the last 15 years. Ingushetia's regional president was badly wounded in a suicide attack in June, and a suicide bombing of a police station in August killed at least 24 people.

Rights activists say that widespread abuses against civilians by police and security forces, including abductions, torture and killings, have contributed to swelling the ranks of militants.

Other North Caucasus provinces also have remained restive.

Police in a rural village of Chechnya said they killed four militants who had been barricaded in a small building with around 20 others. The remaining suspected insurgents attempted to flee, said Magomed Deniyev, a spokesman for the regional branch of the Interior Ministry.

And in the province of Dagestan, police killed three suspected militants in a clash late Wednesday, police spokesman Mark Tolchinsky said.