KIEV, Ukraine — Petro Poroshenko took the oath of office as Ukraine’s president, assuming leadership of a country mired in a violent uprising and economic troubles.

Poroshenko, who became a billionaire as a candy tycoon, was elected on May 25, three months after the pro-Russian president Viktor Yanukovych fled the country in the wake of months of street protests.

In his inaugural speech, Poroshenko vowed to maintain the unity of his country, as the east is embroiled in an uprising by pro-Russian rebels.

Speaking in parliament, Poroshenko promised the residents of the Donbass region, which is largely in rebel hands, that he would decentralize power and guarantee the free use of the Russian language.

Poroshenko promised amnesty “for those who do not have blood on their hands.” That appeared to apply both to separatist, pro-Russia insurgents in the country’s east and to nationalist groups that oppose them.

Poroshenko also promised dialogue with citizens in the eastern regions, but excluded the insurgents. “Talking to gangsters and killers is not our avenue,” he said, according to a translator. He also called for early regional elections in the east.

Taking a hard line against Moscow, however, he said that there would be no compromise with Russia on his pro-European stance and the status of the Crimean peninsula.

“The Crimea has been and will remain Ukrainian,” he said. “I put that clearly to the Russian leader in Normandy,” he added, referring to his meeting with President Vladimir Putin at D-Day commemorations on Friday.

Ukraine's President-elect Petro Poroshenko, right, German Chancellor Angela Merkel, second left, and Russian President Vladimir Putin, left, applaud during the commemoration of the 70th anniversary of the D-Day in Ouistreham, western France, Friday, June 6, 2014. (photo credit: AP/Alexander Zemlianichenko)

Ukraine’s President-elect Petro Poroshenko, right, German Chancellor Angela Merkel, second left, and Russian President Vladimir Putin, left, applaud during the commemoration of the 70th anniversary of the D-Day in Ouistreham, western France, Friday, June 6, 2014. (photo credit: AP/Alexander Zemlianichenko)

Putin has denied allegations by Kiev and the West that Russia has fomented the rebellion in the east, and he insisted Friday that Poroshenko needs to speak directly to representatives from the east.

Poroshenko said in a statement that he expected the Russian parliament to rescind its decision granting Putin permission to use the military on the territory of Ukraine and also wants a joint action plan on sealing the Russian-Ukrainian border.