The Ukrainian military said on December 11 that three Ukrainian soldiers were killed and eight injured in attacks by pro-Russian separatists over the previous 24 hours -- the first casualties since a fresh truce deal in eastern Ukraine went into effect on December 9.
Military spokesman Andriy Lysenko said that Ukraine's army also registered 22 shelling attacks by separatists in the same time period.
In Moscow, Russian Foreign Ministry spokesman Aleksandr Lukashevich said on December 11 that Russia is sparing no effort to convene another round of peace talks.
A cease-fire agreed on September 5 in Minsk has been repeatedly violated, with more than 1,000 people killed since the deal was signed.
A fresh round of talks in Minsk had been expected this week, but the renewed violence has clouded prospects for the resumption of talks.
The truce declared by the Ukrainian government on December 9 was dubbed a "day of silence" and appeared to hold for 24 hours -- with Kyiv announcing on December 10 that it would extend the truce.
It followed a cease-fire agreed in September in the Belarusian capital, Minsk, which has since been repeatedly violated, with more than 1,000 people killed. The total number of deaths since the start of the conflict in mid-April amounts to some 4,300, according to the United Nations.
The two sides -- along with Russian and European monitors -- are still trying to organize comprehensive peace talks.
The Ukraine government had initially hoped to hold talks in Minsk on December 9, and by December 12 at the latest.
But there has still been no announcement of renewed talks.
Meanwhile, both sides have accused the other of delaying negotiations expected to focus on prisoner exchanges, amnesties for separatist fighters, and the future political status of Ukraine's two separatist-dominated provinces in the east.
On December 10, Ukraine's former President Leonid Kuchma -- Kyiv's envoy in the peace process with Russia, separatists, and the Organization for Security and Cooperation in Europe (OSCE) -- said a new round of negotiations should not be held in Minsk in the coming days because separatists had violated a previously agreed cease-fire deal.
But Lukashevich, the Russian foreign ministry spokesman, told a news conference in Moscow on December 11 that "Russia will dedicate the maximum effort to having a meeting of this group organized as soon as possible and bringing about positive results for further steps towards carrying out the Minsk agreements."
Earlier on December 11, Ukrainian President Petro Poroshenko called on Russia to end its support for the separatists, including withdrawing any Russian forces that are on Ukrainian soil.
Poroshenko, speaking during a visit to Australia, also urged Russia to seal the border between the two countries, saying that doing so would lead to "peace and stability in Ukraine" within a matter of weeks.
Moscow denies playing any role in the conflict in eastern Ukraine.
Australia and Ukraine have formed close ties over Moscow's support for the separatists since Malaysia Airlines Flight 17 was shot down in July over rebel-held territory in eastern Ukraine.
Of the nearly 300 people who died in the air disaster, 38 were Australian citizens or residents.
Ukraine's government and many officials in the West blame the separatists for shooting down the plane with a missile supplied by Moscow, something the Kremlin denies.
Australian Prime Minister Tony Abbott said on December 11: "If it turns out that people under Russian authority had a hand in this, we absolutely expect them to be surrendered to investigators and to prosecutors because this is an atrocity. It was mass murder on a vast scale."
With reporting by AFP, Reuters, and Interfax