Media affiliated with the Kurdistan Workers' Party (PKK), a leftist militant group battling the Turkish state, posted a video purporting to show a fighter downing a Cobra attack helicopter with a man-portable air-defense system — or MANPADS — in the mountains of southeastern Turkey on Friday morning. (Gerilla TV)

ISTANBUL — They were used to stalk Russian helicopters in Afghanistan, and the United States has worked hard to keep them out of chaotic Syria. But now Kurdish guerrillas battling Turkey's security forces may now have shoulder-fired missiles — an acquisition analysts say will seriously challenge Turkish air power and potentially intensify fighting in the region.

On Saturday, media affiliated with the Kurdistan Workers' Party (PKK), a leftist militant group battling the Turkish state, posted a video purporting to show a fighter downing a Cobra attack helicopter with a man-portable air-defense system — or MANPADS — in the mountains of southeastern Turkey on Friday morning. Arms observers said this is the first time they have seen PKK fighters successfully using MANPADS in their four-decade fight against the Turks.

About four minutes into the video, the fighter, clad in camouflage fatigues, crouches on a verdant hillside with the weapons system on his shoulder. When the launcher locks on its target — a helicopter whirring noisily on the horizon — the fighter stands to fire. The heat-seeking missile swoops through the air and strikes the Cobra's tail, sending the aircraft spinning and eventually crashing into the mountainside.

Turkish authorities on Friday had attributed the helicopter crash in Hakkari province to an unknown technical failure. The chopper had been dispatched, however, after the militants staged an attack that killed six Turkish soldiers in the area.

"There have been rumors of them having MANPADS in their arsenal, but nothing concrete," said Kyle Glen, co-founder of Conflict News, a website that collects information and images from conflict zones around the world.

"This is the first actual video evidence of their use inside Turkey that I have seen in several years," he said. "Turkey will have to escalate, which means the PKK will escalate in return. … [It's a] bloody cycle."

The PKK has successfully used MANPADS before, including two 1997 strikes that downed two Turkish helicopters in northern Iraq, according to Charles Lister at the Middle East Institute in Washington. "There have been more recent alleged uses," Lister said, "but minimally documented."

Turkey and the PKK have been locked in conflict for more than 40 years over autonomy for the millions-strong Kurdish minority. The Turkish government has long seen the Kurds, who maintain a separate culture and speak a different language, as a threat to the ethnic purity of the Turkish state.

The PKK, however, has carried out a number of bombings against both civilians and security forces throughout the conflict. Last year, a two-year-old truce between the two sides broke down, and the war reignited. Since then, PKK and other Kurdish guerrillas have killed hundreds of Turkish soldiers in clashes and other attacks, including suicide bombings.

But the use of a surface-to-air missile — which arms experts said is likely a Russian-made 9K38 Igla — is a new and troubling development. It's unclear where the militants, who maintain bases in both Turkey and Iraq, would have obtained the weapon system. But former Iraqi president Saddam Hussein was known to have acquired the same Russian-made system in the 1980s, as did Libyan strongman Moammar Gaddafi.

The successful attack "is a game changer" and "could lead to further escalation in the region," Aykan Erdemir, senior fellow at the D.C.-based Foundation for the Defense of Democracies, posted on Twitter.

Turkish officials did not respond to request for comment.