As war rages in Ukraine, more than a thousand miles away in Bosnia observers are warning that Russia is fanning the embers of separatism which could spell trouble for the deeply divided Balkan country.

Since the end of the war that claimed around 100,000 lives between 1992 and 1995, Bosnia has been split between a Muslim-Croat federation and a Serb entity -- known as Republika Srpska (RS). 

But there are growing fears the arrangement that has kept the peace in Bosnia for decades may be at risk. 

Bosnia's Serb leader Milorad Dodik -- who has made no secret about his admiration and close ties with President Vladimir Putin -- has been increasingly vocal about his secessionist aims, a move widely believed to have the backing of the Kremlin. 

The latest sounding of the alarm over the situation came from US Democratic Senator Chris Murphy, who warned of a "very worrying time for Bosnia" during a recent tour of the Balkans. 

"As Putin gets backed into a corner, he is going to look for other places to try to score victories. And one of them may be Bosnia," he told CNN.

For centuries, Russia fostered deep fraternal ties with the Serbs in the Balkans -- undergirded by their Slavic and Orthodox heritage along with their steadfast alliances during the world wars of the 20th century.

NATO's intervention in the Balkans in 1990s -- first in Bosnia and later against Serbia during the Kosovo war -- has long been seen by the Kremlin as a humiliating provocation.

Since then, Russia has sought to increase its influence on the ground with Bosnia's Serbs.  

In statements that echoed Putin's rhetoric ahead of the attack on Ukraine, Moscow's ambassador to Sarajevo warned that it will "react" if Bosnia joins NATO. The embassy also cautioned the West against manoeuvres that could destabilise Bosnia.

Moscow routinely pillories the international high representative in Bosnia -- a posting created to oversee the peace accords that ended the war -- while calling for the position's abolition. 

Russia recently lashed out at "growing attempts to rewrite the principles" of the accords "to the benefit of the EU and NATO and to the detriment" of Bosnia's Serbs.

The RS's continued support for Moscow has also prevented Bosnia from following Western countries in sanctioning Russia after the invasion of Ukraine. 

In March, NATO Secretary General Jens Stoltenberg said Bosnia was among the potential targets of "even more intervention" from Russia.

- Tug of war -
"What is clear is that Russia is now openly breaking with the West in Bosnia," said Florian Bieber, a Balkan specialist at the University of Graz in Austria. 

Western "passivity" has created instability in the country by allowing Dodik to cross several red lines over the years, Bieber added. 

Srecko Latal, editor of regional investigative journalism network Balkan Insight, said outside players had filled a vacuum.

"The Balkans have been destabilised above all by the absence of the EU", which has allowed third parties to step into the breach, he told AFP. 

"The presence of Russia and any other foreign influence -- Chinese, Turkish or some Gulf countries -- is the consequence".

But recently, with Europe on edge, the West has returned to the fold. 

In January, Washington hit Dodik with fresh sanctions, accusing the leader of threatening the stability of the region after he moved to withdraw from the country's central institutions including the army, judiciary and the tax system.

The United Kingdom followed suit in April, accusing Dodik of "deliberately undermining the hard-won peace in Bosnia and Herzegovina" with Putin's encouragement. 

The EU has not imposed sanctions but has nearly doubled its military presence in Bosnia as a "precautionary measure", according to Anton Wessely, commander of the EU Force in Bosnia and Herzegovina.

- 'Natural ally' -
"This Russian threat appears to really have forced the United States and the EU to adopt a more serious approach and to understand the situation in Bosnia and in the rest of the Balkans," said Latal.

For decades, Moscow has fostered vital relationships in the Balkans to maintain leverage in Europe, especially in countries with large Orthodox populations like Serbia, Montenegro, and Bosnia. 

"Russia has enough local infrastructure and local followers throughout the Balkans" to try to destabilise the region further "if it wants to", said Latal.

Meanwhile, thousands of Bosnian Serb war veterans made clear where their allegiances lie during a demonstration in RS's capital Banja Luka earlier this month.

Wrapped in the red, blue and white flag of the RS, Aco Topic, 69, said he would give his life for Dodik, citing his love "for his principles".

"Who else could help us if not Putin," he said, holding a poster featuring Dodik, Putin, and Chinese President Xi Jinping.

"Russia is our natural ally and will never betray us," added Danica Micevic, a 54-year-old civil servant. 

"It is not Russia that wants destabilisation here, it is the West."