DUSHANBE (Reuters) -- Tajik forces have killed five gunmen in a shoot-out near Tajikistan's border with Afghanistan, the latest in a series of attacks on security forces across Central Asia, a security source said.
Instability has been on the rise in past weeks in Central Asia, a Muslim region home to 50 million people, as fighting has intensified in the adjacent areas of Afghanistan and Pakistan.
The trend is a concern to the United States because Central Asia is a key transit route for supplies for its troops fighting the Taliban in Afghanistan.
The latest shoot-out in Tajikistan took place in Tavil-Dara, a town at the heart of the Islamist-led resistance to Tajikistan's Russia-backed government in the 1990s during a five-year civil war in which 100,000 people were killed.
A senior Tajik security source, who asked not to be named because he was not authorized to comment publicly on the matter, said the clash occurred overnight when an armed gang attacked a national-guard post and wounded two servicemen.
"Five attackers were killed by the Tajik national guard servicemen in a fight in Tavil-Dara," the source said.
"All those killed had Russian passports. Judging by their appearances and names, all of them were from the Caucasus." He said the motive of the attackers was not known.
Governments in Central Asia have blamed the latest attacks on the Islamic Movement of Uzbekistan (IMU), a group whose militants have long fought alongside the Taliban in Afghanistan.
Some security analysts have said IMU rebels may have started to trickle back into Central Asia, an impoverished region with porous borders, as Pakistan and the United States stepped up efforts against the Taliban in the south.
Last week, rebel Islamist commander Mirzo Ziyoev
was shot dead in Tavil-Dara after he switched sides and agreed with the government to help it convince another armed gang to surrender.
His killing followed an attack on a police checkpoint. Similar attacks have taken place in other parts of Central Asia this summer, including Uzbekistan. It remains unclear who is behind the attacks
and whether they are connected.
In another clash, Kyrgyz security forces killed three men they described as Islamist extremists in a gun battle in the Ferghana Valley, Central Asia's most densely populated area.
Last week, security officials in Tajikistan said there were five ethnic Chechens from Russia among the detained the members of the gang that had killed Ziyoev.