Following a presidential election on Sunday in which Ukrainians overwhelmingly backed the billionaire Petro Poroshenko, the government in Kiev launched a renewed offensive against pro-Russian separatists in the east that killed more than fifty on Tuesday.

Hours after the polls closed Sunday night, the government carried out airstrikes against rebels in the east of Ukraine, near the Russian border, where they have proclaimed two independent states. Helicopters and warplanes attacked the airport of Donetsk, which separatists had seized on Monday, and paratroopers were flown in to root them out.

In his first news conference after winning the election, Poroshenko promised to invigorate the government’s “anti-terrorist” campaign, saying it should to be able to put down the revolt within hours.

First Deputy Prime Minister Vitaly Yarema later said, “We’ll continue the anti-terrorist operation until not a single terrorist remains on the territory of Ukraine.”

Ukrainian troops previously hesitated to attack the rebels on such a scale, fearing Russian intervention if they did. However, the authorities in Kiev appear to have interpreted the outcome of Sunday’s election — which saw more than 80 percent of Ukrainians voting for candidates that supported their national unity, according to preliminary results — as a mandate for more decisive action.

Russia has proposed turning Ukraine into a federation to give especially ethnic Russians and Russian speakers in the southeast more of a direct say in how they are governed. Authorities in Kiev see this as a ploy to divide the country.

Poroshenko, who owns Roshen, an Ukrainian chocolate manufacturer and one of the world’s top confectionery firms, got more than 54 percent support against 13 percent for his closest rival, former prime minister Yulia Tymoshenko. Turnout was highest in the west of the country which tends to favor closer relations with the European Union. In Donetsk and parts of Luhansk, most polling stations could not open due to the violence.

The two regions are home to most of Ukraine’s heavy industries and account for more than 15 percent of its total gross domestic product. Losing them to either the separatists or Russia would be a crippling blow to a country that is on the verge of bankruptcy six months into a political crisis that began when its former president, Viktor Yanukovich, suddenly pulled out of an association and trade agreement with the European Union in November.

Following months of protests, Yanukovich was deposed in February and replaced by an interim government that signed the association treaty the next month.

Russia subsequently seized Ukraine’s Crimean Peninsula, claiming to support an indigenous uprising there. It also massed tens of thousands of troops on the eastern border of its former satellite state which President Vladimir Putin said last week were withdrawing.