NAZRAN (AP) -- A car bomb exploded near a police vehicle in Russia's troubled North Caucasus region, killing four police officers, witnesses and officials said.

The blast occurred in the center of Nazran, the main city in the violence-plagued Ingushetia region.
The bodies of three people, apparently police, could be seen on the ground before the area was cordoned off, and a fourth person was taken from the scene in an ambulance. Four police officers were killed, the Ingushetia branch of the Emergency Situations Ministry said.
According to the ministry's southern Russia branch, three to five other people, apparently civilians, were injured. The blast occurred after police responded to a call about a suspicious car, the ministry's press service said.
Witnesses said a police vehicle stopped near a parked car, and officers emerged and apparently asked a group of men playing cards nearby about the car. It exploded as the police were getting back into their vehicle, the witnesses said.
It was the second such attack this summer and it deepened fears that Russians in the region were being targeted — possibly to try to increase ethnic tension.
On July 16, an ethnic Russian teacher and her 24-year-old daughter and 19-year-old son were found dead, apparently shot while they slept, in what authorities said may have been an ethnically motivated attack.
The republic's chief prosecutor, Yuri Turygin, said in televised comments that the two attacks were similar and may have been linked.
On Wednesday, Ingushetia President Murat Zyazikov said in Moscow that several suspects have been arrested in the July killings, some of them from neighboring republics in the North Caucasus. He said such killings were aimed ""to make people disappointed and leave"" Ingushetia