Petro Poroshenko has been sworn in as president of Ukraine, setting out a plan to bring peace to the conflict-torn east of the country.

The 48-year-old tycoon, who won the May 25 election, offered political concessions to people in the east and said he did not want war or revenge.

Kiev accuses Moscow of backing armed militants in the eastern Donbass area. Russia denies the allegations. Poroshenko was inaugurated in the presence of dozens of foreign dignitaries - including U.S. Vice-President Joe Biden - in parliament in the capital Kiev.

Poroshenko, the owner of the Roshen chocolates group, took the oath of office and laid out a program for ending the crisis that included an offer of early regional elections in the east and a decentralization of power to the regional administrations.

He said: "I don't want war. I don't want revenge, despite the huge sacrifice of the Ukrainian people." But he added: "Talking to gangsters and killers is not our path."

Referring to a brief meeting with Russian President Vladimir Putin in France on Friday, he said: "I put that clearly to the Russian leader in Normandy."

Poroshenko also said there would be no discussion concerning the territorial integrity of Ukraine. "I will make unity happen," he said.

Poroshenko condemned the rule of former President Viktor Yanukovych, seen by many as pro-Russian, who fled in February after a popular uprising in Kiev. He accused Yanukovych of financing terrorism in the east, saying he was "fully responsible for the situation there today".

After their meeting on Friday, Putin said he liked Poroshenko's approach but would wait to see what he could deliver.

"I can only welcome Poroshenko's position that the bloodshed in eastern Ukraine must be stopped immediately," he said, adding that this had to mean an end to the Ukrainian government's "punitive operation".