A ceasefire between government forces and pro-Russian separatists in Ukraine's east appeared to be largely holding despite accusations by both sides of minor violations of the truce.
A Ukrainian defence official accused rebels in Donetsk of a "series of provocations" after the truce went into effect at 15:00 GMT on Friday.
"They fired on our anti-terrorism units on 28 occasions, with 10 of those coming after the ceasefire," National Security and Defence Council spokesman Andriy Lysenko told reporters on Saturday.
Meanwhile, the separatists accused Kiev's forces of breaking the ceasefire just hours after it was agreed and vowed to pursue their independence drive in the east.
A leading member of the parliament established by the self-proclaimed Donetsk People's Republic said that Ukrainian units had launched several missiles toward rebel positions after the truce went into effect.
"The ceasefire's terms are not being observed," Vladimir Makovich told the AFP news agency.
"At 18:00 GMT on Friday, we saw several missiles launched on the outskirts of the city of Donetsk, and also a heavy armoured column moving from the [neighbouring southwestern region] of Zaporizhia."
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His comments were echoed by the "prime minister" of the People's Republic of Donetsk.
Ukraine, Russia and the Kremlin-backed separatists signed the ceasefire deal Friday in Minsk, the Belarusian capital, in an effort to end five months of conflict in the region.
The negotiators also agreed on the withdrawal of all heavy weaponry, the release of all prisoners and the delivery of humanitarian aid to devastated cities in eastern Ukraine.
Al Jazeera's Paul Brennan, reporting from Donetsk, said: "There have been no gun shots that we had heard. That is certainly a good sign. But that does not mean that both sides are not accusing each other of ceasefire violation."
A previous 10-day ceasefire, which each side repeatedly accused the other of violating, yielded few results at the negotiating table.
US President Barack Obama said he was hopeful the latest ceasefire would hold but was unsure the rebels would follow through and that Russia would stop violating Ukraine's sovereignty and territorial integrity.
Both the US and the European Union have prepared even tougher sanctions against Moscow, and Obama stressed that the most effective way to ensure the ceasefire's success was to move ahead with those measures and maintain pressure on Russia.
According to an EU diplomat, the new measures would target Russia's access to capital markets and trade in arms and defence technology, dual-use goods and sensitive technologies.
The new sanctions were given preliminary approval on Friday night and could be implemented as early as Tuesday.
"If certain processes get under way, we are prepared to suspend sanctions", against Russia, German Chancellor Angela Merkel said.
In a statement published online on Saturday, Russia's foreign ministry condemned further EU sanctions and promised that "there will undoubtedly be a reaction from our side" to any new measures.
In August, Russia passed a sweeping ban on meat, fruit, vegetables, and dairy product imports from the EU, the US and a host of other countries who imposed sanctions on Russia.
Ukraine, NATO and Western nations have accused Russia of backing the separatists with weapons, supplies and thousands of regular troops, a claim Russia denies.
A NATO military spokesman told the AP news agency that the number of Russian soldiers directly involved in the conflict has grown past the alliance's earlier estimate of at least 1,000.
Fighting between pro-Russian rebels and Ukrainian government troops has ravaged the already teetering Ukrainian economy, claiming at least 2,600 civilian lives and leaving hundreds of thousands homeless, according to UN estimates.
Source: Al Jazeera and agencies