"I have decided to cancel the working visit to Turkey in connection with the sharp deterioration of the situation in the Donetsk region, in particular in the Amvrosiyevka and Starobeshevo," he said.
Poroshenko also said a meeting of the National Security and Defense Council would be convened on Thursday to work out a plan of further action.
Ukraine has also asked to convene a meeting of the United Nations Security Council.
"The world must give an assessment to the sharp deterioration of the situation in Ukraine," Poroshenko said.
The Ukrainian president was to leave for Turkey for the inauguration of President Tayyip Erdogan. Poroshenko was planned to have seven bilateral meetings during the visit.