The European Union isn't a "sanctions geyser" and its restrictions imposed on Russia in the wake of the Ukraine crisis should be "proportional and reversible," Italian foreign minister Paolo Gentiloni said Friday.

"The EU is not a sanctions geyser, sanctions are an instrument to a political solution," he said during a meeting in Rome with the foreign media.

Ukraine's foreign minister said Friday that his war-torn country needed a "real" ceasefire, a day after Ukraine and pro-Russian rebels agreed on a fresh truce starting on December 9.

Ukraine needs "a ceasefire not in name, but ceasefire in substance," Pavlo Klimkin told reporters in Switzerland on the sidelines of a meeting of the Organization for Security and Cooperation in Europe (OSCE) focused on the crisis in his country.

Ukraine and the pro-Russian rebels said Thursday they had agreed to halt fire on December 9 under the terms of a truce aimed at ending one of Europe's bloodiest conflicts in decades.

The unexpected announcement provides the latest glimmer of hope that fighting across the eastern rustbelt of the ex-Soviet nation was nearing to a close after eight months that saw 4,300 people  killed and shattered Moscow's ties with the West.

Islamist insurgents launched a brazen attack in the Chechen capital Grozny on Thursday that sparked heavy clashes with security forces, leaving 20 dead and a central market burnt.

Militants barricaded themselves in a school and police cordoned off city streets in violence that erupted just as President Vladimir Putin gave his annual address to the nation, vowing to end violence in Chechnya.

Ukrainian Foreign Minister Pavlo Klimkin stressed Thursday the need for a real ceasefire for eastern Ukraine, and not just the "hybrid" version currently in tatters.

"What we need is not just a hybrid ceasefire (for) the hybrid war. What we need is a real bilateral ceasefire," Klimkin told reporters at the start of a meeting of some 50 foreign ministers from Organisation for Security and Cooperation in Europe countries.

U.S. Secretary of State John Kerry urged Russia Thursday not to isolate itself "through its own actions" as top diplomats grappled with elusive peace efforts in Ukraine but Moscow lashed out at biting sanctions.

President Vladimir Putin accused the West of using the Ukraine conflict as a pretext to restrain a muscular Russia with sanctions and defiantly declared that Moscow would overcome the blow to an economy on the brink of recession.

The Ukraine military reported Thursday more than 70 rebel attacks on its positions in the past 24 hours.

The attacks took place across several parts of the frontline in eastern Ukraine, a military spokesman said, including in Lugansk and the airport in Donetsk, where the two sides have this week tried to put ceasefires in place.

President Barack Obama said Wednesday Russian counterpart Vladimir Putin is unlikely to shift his stance on Ukraine until the full force of economic sanctions levelled against Moscow hits home.

Obama said Putin's "nationalist, backward-looking" outlook had isolated Russia internationally but had played well domestically. 

NATO said Wednesday it will keep military channels of communication with Russia open to avoid any misunderstandings over military activity, as the Ukraine crisis stokes tensions not seen since the Cold War.

The 28 member states of the U.S.-led alliance, set up originally to protect Western Europe from the Soviet Union, "agreed that at this time of tension there is a need for continued communications among NATO and Russian military to avoid any incidents," a NATO press officer said.

Ukraine's military accused pro-Russian fighters on Wednesday of violating a long-awaited truce at a flashpoint airport in rebel-held Donetsk just hours after it was agreed.

The sound of artillery shelling echoed across the war zone's largest city the morning after both sides promised to halt fire at the site of the deadliest fighting in the eight-month east Ukrainian conflict.