Russian authorities are on high alert after six bodies and three explosive devices were found in and around abandoned cars near the site of next month’s Winter Olympics.

Security forces have been deployed in a counterterror operation 186 miles east of Sochi in the Stavropol region, where the bodies and explosives were found Wednesday, according to the BBC.

Two of the three men being sought by police are suspected members of an Islamist militant group and are on a Russian federal wanted list for the murder of a hunter, the BBC reported, citing local media.

Investigators say the six victims appeared to have been shot to death and placed in four cars on the outskirts of the city of Pyatigorsk.

Three of the cars were rigged with explosives, but only one device went off when police went to inspect them, The Guardian reports. No one was injured.

Vladimir Markin, the spokesman for Russia's main investigative agency, said in a statement that no motive had yet been found for the killings. He said one explosive device was placed in a metal bucket next to a car.

Markin said Federal Security Service officers had joined the investigation, which was classified as a counterterrorism operation.

Three men whose bodies were in three of the cars have been identified: Two were taxi drivers and the third assembled furniture for a private businessman, Russian state news agencies reported, citing law enforcement agencies. Their names have not been released. The men were said to be local residents and drove inexpensive Soviet-model Lada cars.

The grisly discoveries came a day after Russia launched strict security measures in Sochi.

Security concerns are high because of a violent Islamist insurgency simmering in the nearby North Caucasus region. Fears were heightened following two suicide bombings last week in the city of Volgograd, about 400 miles away, which killed 34 people and wounded scores.

Although there has been no claim of responsibility for the bombings or the bodies and explosives, the leader of the Islamist insurgency last year, Doku Umarov, called for attacks aimed at undermining the Sochi Olympics.

Tens of thousands of Russian police, security agents, rescue workers and army troops are being deployed for the games, which run Feb. 7-23. Vladimir Puchkov, who heads the Emergency Situations Ministry, said all of his security units for Sochi were on duty as of Tuesday

In addition, all vehicles were banned from the area beginning Tuesday except for those registered in Sochi or with special Olympics passes.

Tuesday was also to be the start of a ban on all demonstrations in Sochi not connected with the games. Russian President Vladimir Putin last weekend rescinded the blanket ban, but any demonstrations or marches still need to be approved by the Interior Ministry, which is in charge of the country's police force.

Putin has spent the past few days in Sochi. Last week, he inspected preparations for the games and went skiing in the mountains near Sochi.

The Associated Press contributed to this report.