Former Ukrainian President Petro Poroshenko said on May 28 that he was barred from leaving the country and accused the government of breaking a so-called political cease-fire in place since Russia invaded on February 24.

Poroshenko was in power from 2014 to 2019, and his European Solidarity party is the second-biggest party in Ukraine's parliament after President Volodymyr Zelenskiy's ruling Servant of the People party.

Poroshenko was elected as the head of a pro-Western government after popular protests in 2014 ousted Russia-backed former President Viktor Yanukovych.

Zelenskiy crushed Poroshenko in a 2019 election on a campaign to fight corruption and curb the influence of oligarchs.

In January, Poroshenko was charged with treason in a case that he and his supporters reject as politically motivated.

The accusations against Poroshenko, one of Ukraine's richest men, are linked to the alleged sale of coal to help finance Russia-backed separatists in eastern Ukraine in 2014-2015, while he was in office.

The case has raised international concern, with U.S. Secretary of State Antony Blinken appealing to Ukrainians in February to “stick together” as the threat of a Russian invasion loomed.

After Russia invaded, Ukraine's parliament banned several pro-Russian parties and allowed others to still operate under a tacit deal under which all parties would put aside domestic political disagreements to unite against the war.

But on May 28, Poroshenko's office said he "was refused to cross the border of Ukraine," accusing the government of violating the agreement.

"There is a risk that by this decision, the authorities have broken the 'political ceasefire' in place during the war...which one of the pillars of national unity in the face of to Russian aggression," his office said.

Poroshenko was due to travel to a NATO parliamentary assembly meeting in Lithuania as part of the Ukrainian delegation and had received official permission to travel.

He was due to meet in Vilnius with Lithuanian President Gitanas Nauseda and a group of European parliamentarians.

He was then to travel to Rotterdam in the Netherlands for a summit bringing together European political parties.