Ukrainian President Petro Poroshenko declared a ceasefire from midnight Saturday, ordering his troops to stop fighting the separatist rebels in eastern Ukraine, media reported.
The separatist Donetsk People's Republic also announced a ceasefire, according to a CNN report.
On Thursday, Russian President Vladimir Putin, French President Francois Hollande, German Chancellor Angela Merkel and Ukrainian President Petro Poroshenko announced a peace deal following 14-hour marathon talks in the Belarusian capital of Minsk.
The deal envisages a ceasefire between the Ukrainian forces and independence-seeking insurgents starting Sunday, followed by the withdrawal of heavy weapons from the front line and constitutional reform to give eastern Ukraine more autonomy.
According to Poroshenko, however, if the separatists did not abide by the ceasefire agreement, he would impose martial law throughout Ukrainian territory, his spokesman Andrey Zhigulin told CNN.
Poroshenko's office said he spoke to German Chancellor Angela Merkel, French President Francois Hollande and US President Barack Obama over the phone in the hours before the ceasefire was due to take effect.
"The Ukrainian President has emphasised the need for monitoring by the (Organisation for Security and Cooperation in Europe) to confirm the ceasefire," a statement from Poroshenko's office said, adding, "Petro Poroshenko and Barack Obama have agreed on further coordination of efforts in case of escalation of the conflict."
The White House said in a statement, "The President (Obama) spoke with Ukrainian President Poroshenko today to express his sympathy for the mounting toll of the conflict in eastern Ukraine and his deep concern about the ongoing violence, particularly in and around Debaltseve."
Debaltseve is a strategically located railroad hub in eastern Ukraine.
Shelling rocked two eastern Ukrainian cities Saturday ahead of a the ceasefire deadline, raising fears that the deal to end the bitter 10-month-long conflict may be in jeopardy.
As a positive sign, however, the shelling stopped shortly after midnight, CNN reported.
