KIEV, Ukraine -- Separatist rebels killed five Ukrainian soldiers in violation of a truce extended by the country's government after the European Union gave Russia three days to quell the insurgency or face deeper sanctions.
Twelve soldiers also were wounded in the attacks by pro-Russian separatists in Ukraine's eastern region, government officials said.
The violence occurred as EU leaders in Brussels demanded on Friday that the separatists, who Ukraine and its allies say are backed by Russia's President Vladimir Putin, abide by a cease-fire that Ukraine's President Petro Poroshenko had extended through Monday. Mr. Poroshenko also called on the rebels to release hostages and start talks to implement a peace plan.
Rebel leaders agreed to the extension, according to news service Interfax. Still, the defense ministry in Kiev said Saturday's casualties occurred in two separate incidents.
"Despite peace initiatives by Ukraine's leadership and a unilateral cease-fire, the situation in the Eastern regions continues to escalate," the defense ministry said in a statement. "Insurgents are ignoring the peace plan to ease the situation in Ukraine's east and keep attacking troops."
Also on Saturday, rebels in eastern Ukraine released eight monitors from the Organization for Security and Co-operation in Europe who had been held hostage since late May, according to accounts from the OSCE and Alexander Maltsev, a separatist spokesman for the self-proclaimed Donetsk People's Republic.
Other people not associated with the OSCE are still being held in the region.
The EU leaders said that failure to meet their demands will result in "further significant restrictive measures" against Russia, according to a statement issued on Friday.
"If no visible progress is made on these points, then we are prepared to take further decisions, including drastic measures," German Chancellor Angela Merkel said after the meeting. "We expect progress to come really in the hours ahead."
The U.S. blames Mr. Putin for supporting rebels and stoking violence the United Nations says has killed more than 400 people in Ukraine, a country of more than 40 million. The U.S. is preparing sanctions against Russia on technology aimed at exploiting and producing oil and gas products, a major part of that country's economy, according to three people briefed on the plans.
The U.S. and European allies imposed sanctions about two months ago on a small number of people and companies close to Mr. Putin.
The Russian government sees the conflict through different lens. The U.S. is pushing Ukraine into conflict with Russia, Russian Foreign Minister Sergei Lavrov said on Saturday, adding that the government in Kiev must consult with those in the country who are seeking more autonomy.
"There are our partners from overseas, our American colleagues who, based on plentiful evidence, still prefer to push the Ukrainian authorities along the confrontational road," Mr. Lavrov said on state-run television.
He also said that while separatists in eastern Ukraine's self-proclaimed republics of Donetsk and Luhansk listen to Moscow, they don't respond to all requests from the Kremlin.
Mr. Poroshenko signed a free-trade pact on Friday with the 28- member EU to bolster solidarity with the richer nations to Ukraine's west. He said the agreement showed Ukraine's "sovereign choice in favor of future membership of the EU."
"We're just looking to modernize our country," Mr. Poroshenko said in an interview in the French daily Le Figaro published Saturday. "We introduce freedom, democracy and rule of law, European values, and we're being attacked because of it."