— When separatists here staged a referendum to break away from Ukraine last month, the vote was mocked in Western capitals as a Soviet-style farce.

But in recent days, the split between southeastern Ukraine and the rest of the country has become all too real.

The gleaming airport terminal that put Kiev a commuter-flight away has been shot to bits, with travel to the capital now marked by a bone-jangling journey past rebel checkpoints. A presidential election held everywhere else in Ukraine did not happen here because of security threats. The governor fled for the same reason.

The region’s solidifying status as an island apart from Ukraine will make it harder to put this country back together again. So, too, will the ambitions of separatists, who see the areas they control as a beachhead in a wider campaign to cleave away half the country under the banner of Novorossiya — New Russia.

The idea, straight from the musings of Russian President Vladimir Putin, has become a rallying cry of insurgents here who see Kiev as an enemy capital and Moscow as their natural ally and benefactor. The proposed new entity even has a flag — one that Americans would instantly recognize as a symbol of separatist rebellion, with its blue bars laid diagonally across a red field.

About 350 recruits are engaged in exercises with Ukraine's national guard in preparation for deployment to the east. (Reuters)

“Just like the Confederacy,” said a smiling Pavel Gubarev, an insurgent leader who calls himself the people’s governor of Donetsk.

The blue-and-yellow Ukrainian flag, meanwhile, is rarely seen in this leafy city of 1 million in the middle of the country’s industrial heartland. To speak out in favor of Kiev is to invite attack from rebels who rule the streets and who have shown a taste for brutality.

Gubarev, like all top officials of the separatist movement here, has an office in this city’s occupied administration building. He has decorated his with photos of Che Guevara and Hugo Chávez, and his aspirations are no less revolutionary than were those of his idols.

“We will destroy corruption and distribute the powers of the oligarchs to the people,” said Gubarev, a boyish 31-year-old who said he ran an advertising agency with 81 employees before appointing himself to lead this region of 4.5 million people.

Ukrainian officials say the rebellion’s true goals are far more insidious. The Donetsk People’s Republic, they say, is nothing more than a prop for Russia as it seeks to spread chaos and dismember Ukraine, a process that they say began with the Russian annexation of Crimea in March. Even if southeastern Ukraine is not formally absorbed into Russia, Ukrainian officials worry that Moscow intends to keep the area in its orbit as a breakaway republic, just as it did with South Ossetia and Abkhazia after the 2008 war with Georgia.

“This horrible thing was started by Putin, and it can be stopped by Putin, too,” said Konstantin Batozsky, a senior adviser to the governor of Donetsk, Serhiy Taruta,who recently decamped for Kiev as security here deteriorated.

Evidence of Russian meddling has mounted in the past week as rebel leaders have acknowledged that many of their fighters are “volunteers” from across the border, although the leaders deny any official Russian backing, as does Moscow. The admission coincides with reports from Ukrainian officials of mounting infiltration from the east, as trucks weighed down with militants and weapons slip across a border that exists on maps but not on the ground.

Up to 500 militants used rocket-propelled grenades and mortars on Monday to assault a border patrol headquarters in the Luhansk region, which is adjacent to Donetsk and has also declared its independence. While the attack was ultimately repelled, Ukrainian officials expect that the insurgents will soon try again.

Ukraine’s government has repeatedly vowed a military operation in the southeast to oust the separatists and restore Kiev’s authority. Petro Poroshenko, the incoming president who was elected in a landslide last month and will be inaugurated Saturday, has said the nation could be reunited within “hours.”

But despite stepping up its campaign against rebels in the insurgent stronghold of Slovyansk on Tuesday, the army has shown little stomach for the sort of urban warfare that would be required to take back the dozens of government buildings across the southeast that have fallen into rebel hands.

Instead, the army has tried to squeeze the separatists, setting up checkpoints around the region’s cities and fortifying its position in the areas it does control.

The strategy may help contain the rebellion and thwart any dreams of reconstituting the 18th-century lands of Novorossiya, which include vast areas of present-day Ukraine. The idea was floated by Putin in April, but analysts say there is not much appetite for it in Ukraine beyond Donetsk and Luhansk.

Other areas of southern Ukraine “are more or less stable, more or less pro-Kiev, more or less anti-Moscow,” said Alexander Motyl, a Ukrainian American political scientist at Rutgers University in Newark. “That doesn’t mean that Chechens, Russians and others won’t or can’t infiltrate them, but the reception is unlikely to be very warm.”

Indeed, outside Donetsk and Luhansk, pro-government oligarchs have set up private armies to ward off the spread of the insurgency. Across northern and western Ukraine, meanwhile, the conflict is an item on the news but hardly a feature of everyday life.

That disconnection has only deepened the sense of isolation for residents here. Up to 15,000 people from Donetsk city have fled — many of them pro-unity Ukrainians who have had to take circuitous routes out of the city to avoid the burgeoning number of rebel checkpoints. Those left behind are forced to keep their views quiet if they do not back the separatists.

At a pro-Russian rally in the downtown Lenin Square on Saturday, hundreds of residents lustily chanted “Rossiya!” as speaker after speaker condemned “the Kiev junta.”

On the edge of the park, in the shade of trees, a 75-year-old retired teacher leaned on his cane and whispered his contempt. “This is a crowd of zombies,” said the man, who gave his name as Anatoliy. “They want a return to the Soviet Union.”

As he spoke, a clutch of pro-Russian demonstrators passed by and grew suspicious. They demanded to know what he had said and loudly berated him for speaking to an apparent foreigner.

As this region’s isolation has grown, so too has its xenophobia, with separatist backers taking their cues from Russian media outlets and blaming the West for the instability.

“We want to kill Obama. It’s all his fault,” said Valentina, a 60-year-old pro-Russian demonstrator who declined to give her last name because, like many here, she suspects Westerners of spying.

Those from other parts of Ukraine are increasingly seen here as foreigners themselves, and the incoming president, Poroshenko, is regarded as the leader of a distant — and hostile — land. Even before he’s sworn in on Saturday, Poroshenko is being denounced here as the commander of a criminal army that is poised to invade.

“The Ukrainian army is killing ordinary people,” said Nicolai Zapaliskiy, a 42-year-old office manager who was at the railway station this weekend with a roller suitcase and a plan to move far away from the turmoil of Donetsk. “I was always proud to be Ukrainian, but now I’m ashamed.”

And with that, Zopaliskiy set off for his new life, on a train bound for Russia.