Four people were injured as a result of an explosion in a southern Russian region, police said Tuesday, RIA Novosti reported.
"Four people were injured in an explosion in Makhachkala. One is in serious condition. All of them are civilians," a police spokesman said.
Makhachkala is the capital of Dagestan, a volatile North Caucasus republic in southern Russia.
The explosion occurred Monday at about 2300 local time [1900 GMT] at an avenue near a marketplace. It damaged two cars parked nearby.
Sporadic terrorist attacks and militant clashes are common in Russia's volatile southern republics, where Russia has held two brutal wars against separatists in the region of Chechnya, although the Kremlin has officially ended its military campaign against separatists and terrorists there.
An investigation is underway. Experts are working to establish where the explosive device was placed.