The Ukrainian army and Russia-backed separatists in eastern Ukraine have accused each other of violating a cease-fire that took effect just a day ago.
The army press service said on December 25 that the separatists had fired 39 times at various government-controlled areas near the front line, despite the truce agreement.
The military said the separatists shelled the Maryinka, Shirokine, Talakovka, and Vodyanoye residential neighborhoods in the Mariupol area.
Ukrainian military positions also came under machine-gun and mortar fire in the Luhansk and Donetsk areas, it added.
Meanwhile, the separatists accused the Ukrainian military of violating the truce more than 220 times since it came into effect at midnight on December 24.
Ukrainian forces shelled 10 residential areas in territory controlled by the group that calls itself the Donetsk People’s Republic, a separatist official said on December 25.
The so-called "indefinite" cease-fire between the two sides was agreed on December 21.
Ukrainian President Petro Poroshenko said the agreement was a sign that his war-weary nation is on the road to a lasting peace after nine previously negotiated cease-fires unraveled.
Self-described leaders of the separatists also said the truce was a sign of hope after a recent sharp upsurge in violence in the Donbas region.
United Nations Secretary-General Ban Ki-moon and German Foreign Minister Frank-Walter Steinmeier said they welcomed what Steinmeier called a "unanimous recommitment" to peace ahead of the holidays.
Orthodox Christmas is observed on January 7.
The two sides agreed to a similar holiday truce last year. It lasted for several weeks before fighting slowly resumed.