* Heavy clashes on Friday near Mariupol port and in Donetsk
* Fighting mostly subsided ahead of 1500 GMT ceasefire
* Residents and combatants sceptical about peace prospects (Updates with signing of ceasefire deal, end of heavy fighting)
By Aleksandar Vasovic and Gabriela Baczynska
MARIUPOL/DONETSK, Ukraine, Sept 5 (Reuters) - Heavy fighting between Ukrainian government forces and pro-Russian rebels appeared to subside after envoys meeting in Minsk approved a peace deal that included a ceasefire taking effect from 1500 GMT on Friday.
Minutes after the ceasefire was due to come into force, three explosions were heard north of the city of Donetsk. It was not immediately clear how serious the blasts were.
Ukraine's President Petro Poroshenko said envoys from Ukraine, the pro-Russian separatist leadership, Russia and Europe's OSCE security watchdog had agreed the ceasefire and a peace plan for the war-shattered region in talks in Minsk.
Fighting had raged for much of the day in two areas of eastern Ukraine - near the strategic port of Mariupol on the Sea of Azov and further north in the rebel stronghold of Donetsk, mainly near the city airport which remains in government hands.
A Reuters reporter heard more Ukrainian shelling of rebel positions east of Mariupol about two hours before the ceasefire was scheduled to start. Under the ceasefire terms, both sides are meant to stay in their current positions.
A Ukrainian military spokesman said the situation in Mariupol "stabilised" after the announcement of the ceasefire.
Kiev says its forces have been trying to repel a big offensive by the rebels to take Mariupol, whose port is crucial to Ukraine's steel exports. It stands about halfway between Russia and the Russian-annexed Crimean Peninsula.
Ukrainian commanders denied separatist claims that their forces had entered Mariupol on Friday.
"(This claim) is not true. We have even driven them back from the positions they held before," said Andriy Lysenko, spokesman for Ukraine's National Security and Defence Council.
A spokesman for the rebels' self-proclaimed 'Donetsk People's Republic' (DNR) told Reuters: "The army of the DNR has partly entered Mariupol. But the city is not taken."
Mariupol became a major focus of concern for Ukraine after the rebels broke out of their main strongholds further north in late August - backed, Kiev says, by Russian regular forces.
Russia denies sending troops and weapons into Ukraine, despite what NATO says is overwhelming evidence to the contrary.
A Ukrainian military spokesman told a daily news briefing in Kiev that about 2,000 Russian servicemen had been killed so far in the Ukraine conflict. There was no way of confirming the figure independently. The United Nations recently put the total death toll in the conflict to date at more than 2,600.
"BETRAYAL"
However, few in eastern Ukraine, wearied by nearly six months of conflict, have much hope that a ceasefire can hold and some said it was a bad idea that would only benefit the enemy.
"A ceasefire would be a disaster, we would lose everything. By fighting, we can resist the invasion and send them back. With a ceasefire, they will consolidate and carry on after a while," said Taras, a Ukrainian soldier, speaking before the announcement of the deal in Minsk.
Another soldier who gave his name as Mykola said Poroshenko - who was attending the second day of a NATO summit in Wales - would be "betraying the country" if he backed a peace plan now:
"If he goes for a peace plan, then all these dead and wounded and exiled and all the homes burned and jobs lost and money lost, it was all for nothing."
In rebel-held Donetsk, where residents mostly tend to blame the Ukrainian side for the conflict, scepticism was also strong.
"I doubt Ukraine would go for any ceasefire. Poroshenko may announce it for the army but there are also the Kolomoisky battalions," said Denis Tikhinov, 22, who worked for a computer servicing firm before it shut because of the fighting.
He was referring to battalions formed by Ihor Kolomoisky, a wealthy businessman and governor of the Dnipropetrovsk region, to help fight the pro-Russian separatists.
"When the first ceasefire was announced by Poroshenko, Kolomoisky said there would be no such thing and gave orders to his battalions to go on destroying the city and civilians."
On Friday, people queued to get water from cisterns, to sign up for humanitarian aid and to withdraw money from the cash machine of one of the few banks still working in Donetsk, which had a pre-war population of about 1 million.
A mosque, shops and schools were among buildings damaged by renewed shelling on Friday morning.
"I have no hope. Poroshenko is a traitor, he makes promises but he's just lying to the people," said pensioner Lidia. (Writing by Gareth Jones; additional reporting by Andrei Makhovsky in Minsk and Pavel Polityuk in Kiev; Editing by Dominic Evans)
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