* Pro-Kremlin authorities leak cash to rebels
* More economic attacks are being planned
ISTANBUL, Jan 25 (Reuters) - Islamist rebels in Russia's southern borderland are planning to hit economic targets and are getting arms and money funneled secretly by sympathisers in Kremlin-backed local authorities, according to the brother of Moscow's most wanted guerrilla.
With a trimmed beard and thinning hair, Vakha Umarov bears a striking resemblance to his brother, Doku Umarov, who calls himself "Emir of the Caucasus Emirate". He aims to create a pan-Caucasus, sharia-based state separate from Russia.
Chechen rebel leader Doku Umarov has claimed responsibility for a number of attacks in Russia, including last November's train bombing between Moscow and St Petersburg which killed 26.
His brother Vakha Umarov, who has lived in Istanbul since 2005, denied he was part of the insurgency but said he had regular contact with his brother and tends six of his children.
Umarov's words offer a rare glimpse into his brother's intentions. The rebel leader is believed to be hiding in the mountains in Chechnya and very rarely gives interviews.
"All the money used (on the insurgency) is from Chechnya. Weapons are not bought," Umarov told Reuters in an interview on in an office building on the outskirts of Istanbul.
The Kremlin views the Caucasus separatist insurgency as fraught with perils in a vast country stretching from the Pacific to the Baltic coasts. It also poses a danger for energy transit routes.
After two bloody separatist wars with Moscow since the mid-1990s, Chechnya now rests on a shaky peace. Chechen leader Ramzan Kadyrov, an ex-rebel turned Kremlin loyalist, has repeatedly said total calm will come once Doku Umarov is dead.
Dressed in a blue windbreaker and jeans, Doku's brother said: "The weapons are collected from Kadyrov's forces ... Kadyrov's ministries give out money to the mujahideen."
He added that the weapons and money feeding the insurgency across Russia's North Caucasus region, which includes Chechnya, Ingushetia and Dagestan, come from those who claim loyalty to Kadyrov, but who are hedging their bets in case of a power shift in the region.
"It's like an investment for the future, when all this is over, they can (tell the rebels) 'I was on your side all along,'" said Umarov, shortly before he interrupted the interview to pray.
A spokesman for Kadyrov refused to comment.
Umarov said there were around 3,000 militants in Chechnya and a total of 5,000 throughout the north Caucasus.
Umarov disputed analysts' suggestions the insurgency had links to al Qaeda.
He confirmed Doku's pledge from August 2009, after his group claimed responsibility for a Siberian dam disaster that killed 75, to launch an "economic war" on Russia.
A statement on a Russian rebel website last August said fighters had been sent across Russia for attacks that would focus on gas and oil pipelines, power plants and electricity lines. Russia said the dam catastrophe was the result of human error and denied it had any terrorist background.
"Of course there are plans for more attacks. He wouldn't speak if he didn't have plans to back himself up. I know him," said Vakha, who spoke in Russian during the interview.
"If he's said it once he won't need to say it again."
Umarov said he helps Chechen refugees in Turkey, many of whom fled because of war and who number approximately 1,500.
Some of the young sons of Chechen refugees are lured to fight in the insurgency, he said. Every year an average of 10-15 returned from refugee families across Europe and Turkey.
Detained last year by security officials in Istanbul, they told him to leave the country for his own safety, but Umarov decided to remain in Turkey.
Three Chechen militants were gunned down in Istanbul over the past year and a half and Vakha said the police made it clear Turkish authorities did not want to deal with another killing.
Turkey has improved ties with Russia in previous years, especially in the energy sector, with Moscow providing Turkey some 60 percent of its gas needs.
But Umarov said he planned to stay in Turkey unless called back home to fight.
"I'm not needed there yet," he said.
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