The cease-fire in Ukraine was generally holding after its first 24 hours despite reports of scattered violations and continued shelling in the area around the town of Debaltseve.
The shelling by pro-Russian separatists of Debaltseve is the main point of concern regarding the cease-fire, as a commander for the rebels told Reuters that his forces could open fire on the town and territory around it because "it is our territory."
The Organization for Security and Cooperation in Europe (OSCE), which is responsible for monitoring the cease-fire, said the separatists had blocked OSCE observers from going to Debaltseve.
OSCE spokesman Michael Bociurkiw said on February 15 that the large majority of truce violations had occurred around the Debaltseve area but some also near the rebel cities of Donetsk and Luhansk.
Occasional explosions were also heard outside of the southern port city of Mariupol.
The Ukrainian military said on February 15 that separatists were using various weapons, including Grad rocket systems, to attack Debaltseve.
Ukrainian President Petro Poroshenko said the cease-fire agreement that was signed in Minsk on February 12 was "threatened" by the situation around Debaltseve.
Speaking via phone with the leaders of Germany, France, and Russia on February 15, Poroshenko said the position of the four at peace talks last week in Belarus had been for a cease-fire everywhere, including Debaltseve.
He added that he would introduce martial law across the country if the cease-fire failed to take hold.
A Ukrainian government spokesman said Kyiv's forces had come under fire about 10 times since the midnight cease-fire but that all shelling was "localized" and no service personnel had been killed.
A Ukrainian military spokesman said Kyiv had prepared storage areas for heavy weaponry that is due to be removed from the line of conflict between the government and Russia-backed separatists in eastern Ukraine.
A spokesman for the separatists likewise said they had begun "to draft a plan on the withdrawal of heavy armaments and the exchange of prisoners."
U.S. Secretary of State John Kerry spoke by telephone with Russian Foreign Minister Sergei Lavrov and emphasized "the importance of full implementation" of the Minsk agreement.
Kremlin spokesman Dmitry Peskov said the Minsk agreement must be "unconditionally observed" by all sides, but he made no mention of whether Moscow believed the truce applied to Debaltseve.
Ukrainian forces in Debaltseve -- which is an important transport hub between the rebel-held cities of Donetsk and Luhansk -- have been staving off the Russian-backed separatists for weeks.
The rebels claim to have completely encircled the town and, in the process, thousands of Ukrainian troops.
But Ukraine says its forces have kept a road open that is used to resupply its forces as they face the shelling and missile attacks.
Washington says regular Russian forces along with tanks and multiple-missile launchers converged on Debaltseve in the days before the cease-fire.
Reuters journalists located on the rebel side have seen armored columns of troops who were not wearing any insignias arriving in the area in recent days.
Russia denies supporting the rebels and says it has no troops in Ukraine.
The UN is currently negotiating a Russian-drafted resolution that would welcome the Minsk truce agreement and call on all parties to implement it.
The cease-fire is to be the first step of a peace plan designed to end 10 months of conflict that has killed at least 5,350 people and caused hundreds of thousands more to flee their homes.