* Islamist group condemns Russia over Sochi games
* Russia's North Caucasus rocked by insurgency
* Militants threaten more attacks in Russia (Adds online video)
By Timothy Heritage
SOCHI, Russia, Feb 11 (Reuters) - A militant Islamist group has urged followers to pray for an earthquake in Sochi during the Winter Olympics to avenge Muslims who died there fighting "Russian infidels".
The appeal was made by a local branch of the Caucasus Emirate, a group which is waging an insurgency for an Islamist state in Russia's North Caucasus and called on supporters last year to attack the Games.
"All who are able to read this letter can supplicate that the Almighty destroys the land in Sochi with an earthquake, and makes the infidels 'drunk of water' before Hell and drown in a flood!," said the appeal posted online on Monday.
"The Games of the atheists and pagans! The pigs are so arrogant that they decided to host the Games on the ground where our ancestors shed their blood to defend Islam and Muslims. Even the blind can see it!"
Russian President Vladimir Putin, who waged a war in Chechnya to try to rein in separatists in the North Caucasus, has staked his personal and political prestige on the Games.
But some of the events are being held in territory that was the homeland of ethnic Circassians until they were expelled in the 19th century.
Islamist leaders say this amounts to performing "Satanic dances" on the graves of Muslims killed fighting Russian forces and one, Caucasus Emirate leader Doku Umarov, urged followers last year to prevent the Games going ahead.
"We know how the Russian infidels - those who we have been fighting for centuries in the Caucasus - have become arrogant and decided to hold the Satanic Games on the ground of the companions who brought Islam," said the new appeal, issued by the Ingushetia media branch of the Caucasus Emirate.
"May Allah give the infidels in Sochi the last earthquake of their lives," it said.
Ingushetia lies about 650 km (400 miles) by road from Sochi across the Caucasus mountains.
Russia says the Games are as safe from militant attacks as anywhere in the West and Russian security services are working with colleagues from Europe and North America.
The insurgency in the North Caucasus, which stretches from Dagestan on the Caspian Sea to near Sochi's coast on the Black Sea, is rooted in the wars between Russian forces and Chechen separatists in 1994-96 and 1999-2000.
The Caucasus Emirate said separately in a video posted online that it was responsible for the deaths of six people last month in the Stavropol region, a gateway to the North Caucasus, although it said the killings were not related to the Games.
The discovery of the six corpses in cars last month prompted Russia to put security forces on combat alert in the region, about 300 km from Sochi.
A man identified in the video as Emir Tengiz, a Caucasus Emirate leader, accused Russian forces of frequently covering up the murder of peaceful Muslims by saying they were militants and threatened more attacks to drive out ethnic Russians.
"We declare to these infidels that if they do not ... stop killing peaceful Muslims, we will cause such an exodus of the Russian-speaking population that no actions, no investment and no job creation can stop," he said. "We have warned you." (Additional reporting by Steve Gutterman in Moscow, editing by Ed Osmond)