Russia wary of attacks by rebels returning from Syria

BISHKEK (Reuters) - Russia estimates that about 200 of its citizens are fighting alongside Syrian rebels and fears that they could carry out militant attacks once they return, the head of its main security agency said on Wednesday.

Russia has sold arms to Syrian President Bashar al-Assad and lent him crucial diplomatic support during a conflict that has killed more than 80,000 people, but militants from Russia's mostly Muslim North Caucasus are fighting on the other side.

Once the war in Syria is over, foreign fighters returning home "will naturally pose a particular threat to their native countries," Federal Security Service (FSB) chief Alexander Bortnikov said.

He was speaking at a meeting of security agencies of former Soviet republics in Kyrgyzstan's capital, Bishkek, as Russia's foreign minister met his U.S. counterpart in Sweden to talk about a peace conference for Syria where Washington supports the opposition.

Islamist militants have emerged as some of the most effective of the anti-Assad rebels and Moscow has warned Western and Arab backers of the opposition that a post-Arab Syria could fall into the hands of such groups.

The security chiefs from the ex-Soviet republics discussed ways to ensure security at events including the 2014 Winter Olympics next February in the Russian city of Sochi, not far from the North Caucasus.

Bortnikov said that, in addition to the Syrian conflict, the war in Afghanistan and plans for the withdrawal of most foreign combat troops from there by the end of 2014 were a draw for militants.

The two brothers accused of bombing the Boston Marathon on April 15, killing three people and injuring more than 260, were ethnic Chechens who had lived in Kyrgyzstan and the North Caucasus before their family moved to the United States.

Several citizens of Kyrgyzstan have joined the rebels in Syria, the head of the Kyrgyz security service GKNB, Beishenbai Zhunusov, told reporters. He declined to elaborate.

(Writing by Dmitry Solovyov; Editing by Robin Pomeroy)