Story highlights Militant leader killed in police shootout in Dagestan, state media reports

A flier gives details of two more "black widow" suspects sought by authorities

A third woman on the flier was killed in a weekend gun battle in Dagestan

Islamist militants have threatened to strike at the Olympic Games next month in Sochi

Police killed a suspected militant leader in a shootout in Russia's restive republic of Dagestan, state media said Tuesday, amid increasing security concerns ahead of the Winter Olympics in Sochi.

It's also emerged that Russian authorities are hunting two more 'black widow' suspects -- a notorious type of terrorist that's emerged in Russia's clashes with Chechen separatists.

The latest incidents have fueled debate over security at Sochi, despite assurances from Russian President Vladimir Putin that Russia will do its utmost to keep the Games secure.

There have been years of unrest linked to an Islamist insurgency in Dagestan and the North Caucasus region, and Islamist militants have vowed to strike at the Games.

Russian terrorism officials named the suspected militant killed Tuesday in Dagestan as Eldar Magato, state news agency RIA Novosti reported.

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Earlier, the news agency said Russian special forces were engaged in two operations in Dagestan, which lies about a 12-hour drive from Sochi on the other side of the Caucasus Mountains.

Security forces killed three more suspected militants in Dagestan on Monday, it reported.

'Black widows'

Meanwhile, a flier handed out by security forces to hotels in Rostov-on-Don, southeast Russia, names three women it says could carry out a suicide attack planned by militant groups between January 21 and 24, during the Olympic Torch Relay.

One of the three, Zaira Nizamudinovna Alieva, was killed in a gun battle over the weekend in Dagestan in which seven militants reportedly died. She had been trained to be a suicide bomber, RIA Novosti cited terrorism officials as saying.

The other two are named as Djannet Kurbanismailovna Tcakhaeva and Oksana Albertovna Aslanova.

The pictures on the flier show two of the three women in Islamic headgear. But its text warns that the women may not be dressed that way.

"Suspected terrorists may use regularly clothing without any Islamic elements, e.g. no long dresses, no hijab, which makes it easier to blend into a crowd, and makes it easier to get access to large gatherings without being noticed," it says.

Sochi suspect

Police have also handed out fliers at Sochi area hotels warning of a woman they believe could be a terrorist and who now may be in the Black Sea resort town.

One flier seen by CNN asks workers to be on the lookout for Ruzanna "Salima" Ibragimova, described as the widow of a member of a militant group from the Caucasus region.

The woman, according to the flier, may be involved in organizing "a terrorist act within the 2014 Olympic region."

CNN obtained a copy of the flier, which is dated January 15, from security staff at a hotel in Sochi. The flier says authorities have received information about Ibragimova's possible arrival in the region last week.

Photos of Ibragimova have flooded television and social media reports from Sochi, and some describe her as a "black widow."

Many of them are widows of insurgents killed by government forces, and they've been blamed for high-profile suicide bombings

Security experts stressed Monday that Ibragimova was probably one of many suspects that authorities are trying to find.

"I guarantee, they're talking about this one black widow," former CIA officer Mike Baker said, "but there are others that they're also worried about."

In a video that surfaced Sunday, two young men believed to have been suicide bombers in last month's back-to-back bombings in the Russian city of Volgograd made an ominous promise.

"We've prepared a present for you and all tourists who'll come over," the video says. "If you will hold the Olympics, you'll get a present from us for the Muslim blood that's been spilled."

The U.S. military has contingency plans in place for an evacuation of U.S. citizens in case of a major incident in Sochi.