The announcement came as a bit of a surprise given the escalating tensions between the two countries in recent weeks. Fighting in the Donbas region sparked after Ukraine and the West accused Russia of sending troops into the region to support pro-Russian separatists.
Poroshenko's office announced the cease-fire from the Donbas region after Poroshenko spoke with Russian President Vladimir Putin on the phone.
"The conversation resulted in an agreement about a cease-fire regime in Donbas. There was a mutual understanding achieved about steps that will promote the establishment of peace," the Ukrainian president's office said in a statement.
Poroshenko and Putin seem to have taken a different message from the phone call as the Kremlin has denied claims of any cease-fire agreement. It said as Russia is not party to the conflict -- contrary to popular belief -- it has no involvement in any cease-fire agreement. Pro-Russian separatists told Russian news agencies they were not notified before the cease-fire announcement.
Kremlin spokesman Dmitry Peskov told state-run Rossiya 24 that Ukraine and the pro-Russian separatists had not reached an agreement, but discussed the steps needed for lasting peace. Peskov adamantly denied any Russian involvement and asserted the country had no control over the rebel factions.
It is unclear whether the separatists will stand by the cease-fire. Russia and Ukraine have been discussing concessions they would like from the other party, but some issues like autonomy for the separatists and a Ukrainian promise to not join NATO are points of contention.
"The viewpoints of the presidents of the two countries largely coincide on possible ways out of the grave crisis situation," said Peskov.
NATO leaders will be meeting in Wales on Thursday for a summit where they will discuss the crisis in Ukraine and the appropriate response to Russian "aggression."