* Bill would impose jail terms of up to 20 years
* Critics say president clamping down on dissent
Russian lawmakers introduced legislation on Friday that would make spreading separatist views or expressing sympathy for separatist groups a criminal offence punishable by jail.
The bill submitted to the State Duma, Russia's lower parliament house, would establish jail terms of up to six years for spreading "separatist propaganda" and in some cases up to 20 years for planning or publicly calling for action that would threaten Russia's territorial integrity.
President Vladimir Putin weathered big protests by liberal urbanites to win a third Kremlin term in 2012. He has since increased calls for patriotism, stepped up appeals to conservative values and signed several laws that opponents say are intended to stifle dissent.
Russia defeated separatist rebels in the North Caucasus province of Chechnya in a war during Putin's first presidential term, which started in 2000, and is still fighting insurgents who want to carve out an Islamic state in the region.
Putin has repeatedly accused foreign rivals of trying to weaken Russia or tear it apart, including by fuelling Muslim separatism, and has accused the United States and its allies of meddling in Moscow's affairs and backing Kremlin opponents.
"In conditions of increased pressure on Russia, we must arm the law enforcement system with additional instruments to fight separatism," Yevgeny Fyodorov, a lawmaker from Putin's United Russia party and a sponsor of the bill, told Ekho Moskvy radio.
The bill is likely to cause concern that it could be used to silence opposition voices.
Its submission comes after a liberal journalist and Kremlin critic faced ire from United Russia lawmakers last month over a remark about the possibility that Russia could be split apart at the Ural Mountains, which divide Europe and Asia.
Some Russians have expressed concern that faster-growing, more populous China could encroach on Russian territory in the sparsely populated reaches of Siberia, east of the Urals and north of China's border. Putin has shrugged off such fears.
It was unclear when parliament would discuss the bill, which requires three votes in the Duma and one in the upper house before going to the president for his signature. Legislation backed by United Russia is rarely rejected.
Putin has ruled Russia since 2000, either as president or prime minister. Since his return to the Kremlin, he has backed laws tightening legislation on defamation, increasing fines for protesters who step out of line and imposing restrictions on foreign-funded non-govenmental organisations.
The president has denied cracking down on dissent, but has said Russia needs order and discipline.