He said during commemorative events on the Remembrance Day of Crimean Tatars deportation on May 18, Censor.NET reports citing Ukrainski Novyny.
"I am certain Crimea will be de-occupied. I am certain criminals will be punished. The criminal country will be forced to return what it stole," he said.
Poroshenko believes Ukraine's progress in European integration, including visa-free travel granted with he EU countries, will be an important factor for the return of the occupied areas under Ukrainian sovereignty.
The head of state said Ukrainians believe Crimea is Ukraine, and this belief is supported by the international community.
Yesterdaty, Poroshenko annouced he had awarded the title of Hero of Ukraine to murdered Crimean Tatar Reshat Ametov, who was brutally killed in March 2014, following the Russian annexation of the peninsula.
Related materials: Occupied territories - Crimea and Donbas