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. Last Updated: 07/27/2016

Troops Put on Alert in North Caucasus

VLADIKAVKAZ, North Ossetia -- Federal forces in and around Chechnya have been put on high alert in anticipation of new rebel raids following the suicide truck bomb attack on the FSB's Ingush headquarters that killed three people, officials said Tuesday.

A truck carrying 800 to 1,000 kilograms of explosives blew up Monday outside the three-story building, killing two people at the scene in addition to two alleged attackers and injuring at least 25.

A third victim died overnight in a Vladikavkaz hospital, doctor Aslan Bekurov said.

The Emergency Situations Ministry in southern Russia said three patients remained in serious condition on Tuesday.

An Ingush Interior Ministry official, speaking on condition of anonymity, said Tuesday that a man was driving the truck bomb and a woman was in the cabin. The official said that as the truck approached the building, its horn was blaring in an apparent bid to get the building's staff to come to the windows. Itar-Tass, citing a source in the investigation, reported that the truck was registered in Chechnya.

The suicide attackers were not counted in the official death toll.

Ingush Interior Ministry spokesman Yahiya Khadziyev said a third person, who allegedly monitored the strike from a safe distance, was being sought.

There was no immediate claim of responsibility for Monday's blast. Officials called it a terrorist act but did not say who they believe was behind it.

The force of the blast blew out all the building's window panes and ripped open part of the roof. Overturned cars lay crumpled near the pockmarked building in Ingushetia's capital, Magas, and nearby buildings were also damaged.

The Federal Security Service had been leading the federal campaign against Chechen rebels but recently handed control over to the Interior Ministry -- a shift officials called a sign that the situation in Chechnya was becoming more stable.

The bombing in Ingushetia, which has close ethnic ties to Chechnya and shelters tens of thousands of Chechen refugees, came ahead of a planned Oct. 5 presidential election in Chechnya.

The Kremlin has touted the vote as a key step toward peace, but the campaign has been tarnished by accusations of intimidation tactics by supporters of Moscow-appointed Chechen leader Akhmad Kadyrov.

Military and police units in and around Chechnya have been put on high alert after Monday's attack, said an official with the Kremlin-appointed Chechen civilian administration, who spoke on condition of anonymity.

He said at least 10 federal servicemen and police officers were killed since Monday in the latest rebel raids and land mine explosions throughout Chechnya.