Kiev: A two-day-old truce in Ukraine was under threat Monday with fighting unabated around a strategic railway hub and other violations reported, putting in peril an agreement to start withdrawing heavy weapons from the frontline.
The European Union, which backed the fresh peace effort brought about last week through hard-won mediation by France and Germany, pleaded that "the shooting needs to stop".
The bloc also imposed fresh sanctions on Russia, which it accuses of militarily backing the pro-Russian rebels fighting Ukraine`s government troops in a bid to carve out separate republics in the east.
Russia, which denies involvement, vowed an "appropriate response" to the EU move.
Kiev officials and rebels accused each other of ongoing attacks that prevented them from pulling back tanks, rockets and artillery from the frontline in Ukraine`s east, near the insurgent-held cities of Donetsk and Lugansk.
The withdrawal of heavy weapons was meant to begin by midnight (2200 GMT) Monday.The worst of the violence was happening around the town of Debaltseve, a key transport hub between Donetsk and Lugansk, where thousands of government troops were mostly surrounded by heavily armed rebels.
"Non-stop explosions" were heard there on Monday, said Natalia Karabuta, a municipal official who had fled the town. She added that around 5,000 civilians were trapped inside Debaltseve with little food and water.
An Organization for Security and Cooperation in Europe team tasked with monitoring the ceasefire has been unable to enter Debaltseve because of the ongoing hostilities.
A Ukrainian military spokesman, Vladyslav Seleznyov, said "there is no question at the moment of us withdrawing heavy weapons" because of persistent rebel attacks.
Foreign Minister Pavlo Klimkin said Ukrainian troops "are fully observing the ceasefire" but have been attacked 112 times by the separatists. Other officials said five Ukrainian troops have been killed and 25 wounded since the truce came into force on Sunday.
The rebels also rejected any heavy weapons pull-back on their side until a "full" ceasefire was in effect, according to a "defence ministry" spokesman, Eduard Basurin, quoted by a separatist news agency.
Both sides accused the other of renewing attacks on their positions in some other areas, including at rebel-held Donetsk airport and near the port city of Mariupol.Regardless of the fraught situation, European officials described the ceasefire, aimed at ending the 10-month-old conflict that has killed more than 5,600 people, according to the UN, as being generally complied with.
It "appears to be largely holding despite a number of incidents," European Commission spokeswoman Maja Kocijancic said in Brussels on Monday.
However she remonstrated that "it is imperative the ceasefire is fully implemented. A ceasefire is a ceasefire; it means the shooting needs to stop."
A previous ceasefire agreed in September stalled within days and eventually disintegrated.
Earlier Monday, the EU announced additional sanctions on Moscow, adding two Russian deputy defence ministers, Anatoly Antonov and Arkady Bakhin, to its travel-ban and asset-freeze blacklist for allegedly sending Russian troops and materiel in to support the Ukrainian insurgency.
Three other Russians, including two lawmakers, and 14 Ukrainian rebel military or political figures were also blacklisted, along with nine organisations. The sanctions were agreed last month but had been put on hold while France and Germany worked to secure the ceasefire.Western relations with Moscow are plumbing Cold War lows since Russia annexed Ukraine`s Crimea peninsula last year.
Europe and the US have dismissed Russian President Vladimir Putin`s denials of having a hand in Ukraine`s eastern insurrection and noted that he made similar protestations over Crimea before finally admitting he had ordered in Russian troops there.
Western sanctions have targeted those close to Putin and, along with a painful slump in oil prices, accelerated the Russian economy`s slide into recession.
Russia`s foreign ministry on Monday lashed out at the latest round of EU sanctions as "inconsistent and illogical" and said the measures "look particularly ridiculous" after the ceasefire agreement Europe eked out last week.
"Such decisions... will be followed by an appropriate response," it warned in a statement.
Russia has already banned European food imports in retaliation for previous sanctions.