Ukraine government forces on Saturday accused pro-Russian separatists of using Grad multiple rocket launchers overnight in the country's war-torn east in violation of a truce deal signed last month.

Military spokesman Andriy Lysenko told reporters that separatists fired the heavy weapons towards the village of Novotoshkivka from their Lugansk stronghold.

Vandals Saturday destroyed an improvised memorial created by supporters of Russian opposition leader Boris Nemtsov on the bridge where he was shot a month ago, the Echo of Moscow radio station reported Saturday.

Supporters had regularly refreshed flowers and candles on the bridge next to the Kremlin where the 55-year-old former deputy prime minister and prominent critic of President Vladimir Putin was gunned down on February 27.

Even as he breaks down in tears, judge Alexander Klyanoshkin admits no regrets about ending a decade on the bench in his government-held hometown in eastern Ukraine to serve in the pro-Russian breakaway republic of Donetsk.

Along with his wife and children, Klyanoshkin made the 50 kilometers (30 miles) journey south to sign up as a judge in the fledgling court system being established by rebels in their war-scarred capital. 

Fighting close to the strategic eastern Ukraine port of Mariupol, the last major city in the conflict zone controlled by Kiev, claimed one civilian life overnight, police loyal to the government said Friday.

"A male inhabitant of Shyrokyne village died after suffering injuries in shelling" by pro-Russian separatists, Viktoriya Guts, a spokeswoman for Donetsk regional police, told Agence France-Presse.

A default by Ukraine on $3 billion in debt to Russia this year could threaten the International Monetary Fund's lifeline to the embattled country, an IMF spokesman said Thursday.

The Ukrainian government has begun negotiations with creditors for $15 billion in debt relief, part of a $40 billion, four-year financial rescue envisioned by the IMF.

Four people were killed and 20 injured when a passenger bus hit a landmine near a government-controlled town in eastern Ukraine, local officials said Thursday.

The bus had taken a side road in order to avoid a government checkpoint near the town of Artemivsk, some 50 kilometers (30 miles) north of the separatist stronghold of Donetsk, late Wednesday, said Ilia Kiva, a government-loyal deputy police chief in the Donetsk region. 

The United States fears that Moscow and pro-Russian separatists will reignite the armed conflict in eastern Ukraine following a February ceasefire that has largely held, a U.S. diplomat warned Wednesday.

"Russia can reignite the conflict at any time of its choosing," the senior State Department official told journalists.

Mass abductions of children by groups like Boko Haram and the Islamic State are on the rise, with the practice now becoming a tactic of war, a U.N. envoy warned Wednesday.

Leila Zerrougui, the special representative for children and conflict, urged the Security Council to punish armed groups who target children with sanctions and strengthen measures to protect children in conflict.

Ukraine on Wednesday dramatically arrested two top officials on graft charges at a televised cabinet meeting hours after the president sacked a powerful oligarch as regional governor.

The dramatic shake-up came as the beleaguered authorities, already struggling to combat pro-Russian separatists in the country's east, tried to make good on pledges to tackle rampant graft and curb the influence of the country's powerful business magnates.

Ukraine's president has dismissed one of the country's most controversial tycoons from his regional governor's post, his office said Wednesday, in a showdown baring the infighting between powerful oligarchs even as the country struggles to combat pro-Russian insurgents.

President Petro Poroshenko -- himself a billionaire magnate -- accepted Igor Kolomoisky's offer to step down as head of the strategic central Dnipropetrovsk region, the presidency said, after a dispute over control of the main state oil and gas firm descended into open confrontation.