By Gareth Jones and Aleksandar Vasovic
KIEV/MARIUPOL Ukraine (Reuters) - Five Ukrainian servicemen have been killed in the past four days, the military said on Tuesday, underscoring the strains in a ceasefire between government forces and pro-Russian separatists that officials insist is still broadly holding.
The ceasefire, agreed on Friday, is part of a peace plan meant to end a five-month conflict that has killed more than 3,000 people and caused the sharpest confrontation between Russia and the West since the Cold War.
Russia, accused by Kiev and the West of sending troops into eastern Ukraine and arming the rebels, urged the two sides in the conflict to begin talks soon on the region's final political status. It denies accusations of intervening in the conflict.
Under the terms of the ceasefire, Ukrainian military spokesman Andriy Lysenko said the rebels had so far released 648 prisoners-of-war to the government side. He said the Ukrainian side was working to secure the release of a further 500 POWs.
A rebel leader, Andrei Purgin, told Interfax news agency he expected an exchange of 36 more POWs on Tuesday.
The ceasefire largely held overnight into Tuesday despite sporadic violations, including in rebel-held Donetsk, the region's largest city, where government forces hold the airport. A woman was wounded in Donetsk overnight, officials said.
Lysenko said the death toll among servicemen since the start of the ceasefire now stood at five, with 33 wounded.
At the weekend, one woman was killed and at least four other civilians were wounded when government forces came under heavy shelling near the port of Mariupol on the Sea of Azov.
Both sides say they are observing the ceasefire and blame each other for any violations.
"Russian troops and terrorists are continuing their brazen violations of the conditions of the ceasefire, shooting at the positions of the Ukrainian forces, including with heavy weaponry," defense analyst Dmytro Tymchuk, who has close ties to the Ukrainian military, said in a statement.
Speaking in Moscow, Russian Foreign Minister Sergei Lavrov accused the Ukrainian forces of preparing a strike against the rebels, based on what he said were reports of a "heavy concentration" of troops in an area northeast of Donetsk.
Lavrov also said Moscow hoped talks could start soon on the status of southeast Ukraine, where the rebels have declared two "people's republics" outside Kiev's control.
Kiev has said it could grant greater autonomy to the mainly Russian-speaking region, which is home to much of Ukraine's heavy industry and accounts for about 18 percent of its economic output, but firmly rules out independence.
Russian Prime Minister Dmitry Medvedev was quoted on Tuesday as saying his government would support domestic firms targeted by Western sanctions over Russia's role in Ukraine.
The European Union formally adopted a package of new sanctions targeting Russia's energy sector on Monday but said their entry into force would be delayed to allow time to assess whether the ceasefire in Ukraine was working.
One of the key factors driving Western anger over Moscow's role was the downing of a Malaysian airliner over eastern Ukraine in July. All 298 people on board were killed. The West blamed the separatists, saying they were using advanced Russian weapons. Russia denied the allegation and blamed Ukraine.
The Dutch Safety Board said on Tuesday Malaysia Airlines flight MH17 had broken apart due to impact from a large number of fragments, in a report that Malaysia's prime minister and several experts said suggested it was shot down from the groundThe report did not assign blame.[ID:nL5N0RA1AM]
In eastern Ukraine, Mariupol, the main flashpoint along with Donetsk, was quiet on Tuesday, one day after President Petro Poroshenko paid a brief visit to show solidarity with a city the rebels had appeared intent on capturing before the ceasefire.
Poroshenko told cheering residents on Monday he had ordered reinforcements to the city and promised to deal a "crushing defeat" to rebels massed nearby if they tried to advance again in violation of the ceasefire deal. [ID:nL5N0R914C]
"After that bombardment (on Saturday night) we have had two quiet days and I am hoping it will stay that way. This war is taking its toll on everyone and I am hoping this will end soon," Evgeny, a 22-year-old student, told Reuters on Tuesday.
Not everybody was impressed by Poroshenko's visit to Mariupol, which is important for Ukraine's steel exports but lies in the largely Russian-speaking region of Donetsk where many people blame Kiev, not the rebels, for the conflict.
"Poroshenko came yesterday to scare people, to talk about cannons and rockets. To me Ukraine is ready to break the ceasefire and keep on shooting its own citizens, Kiev will be responsible if this town is destroyed," said pensioner Leonid.
(Additional reporting by Gabriela Baczynska in Donetsk and by Amsterdam and Moscow bureaux; Writing by Gareth Jones; Editing by Ralph Boulton)