by Nina Achmatova

One death was reported yesterday in Mariupol. In Donetsk, as the day ended calm fell on the city after shelling caused fires. With the West threatening new economic sanctions, Medvedev threatens to close Russian airspace to Western airliners.

Moscow (AsiaNews/Agencies) - As gunfire and shelling in eastern Ukraine threatened the fragile ceasefire agreed on Saturday by Kyiv, the Kremlin and pro-Russian separatists, Moscow warns of an "asymmetric" response against the West in the event of new sanctions.

Less than 48 hours after the Minsk agreement, reports indicate that pro-Russian rebels shelled the eastern approaches to Mariupol - a major port on the Azov Sea - killing a civilian.

Fresh fighting was also reported at the Donetsk airport, with both sides blaming each other. The city is still a separatist stronghold, but the airport is in the hands of government forces.

The member of observer team from the Organisation for Security and Co-operation in Europe (OSCE) said most of the firing was outgoing from the airport, causing some fires in villages nearby but stressed that was not sufficient to actually make the ceasefire collapse.

The two cities then turned quiet, with no reports of clashes overnight.

Fighting in the east has killed some 2,600 people since April. Yesterday, a Ukrainian official said that 864 Ukrainian soldiers had been killed since the conflict began.

A new report by Amnesty International accuses all sides in the conflict of committing war crimes. The human rights group said civilians had accused Ukrainian government troops of shelling their neighbourhoods indiscriminately. Witnesses also said that separatist fighters had "abducted, tortured, and killed their neighbours".

The report also accuses Moscow of explicitly helping pro-Russian militias in eastern Ukraine, a charge Russian authorities continue to deny.

Meanwhile, in Donetsk and Luhansk, separatists still want to break away from Ukraine even if secession is not part of the peace plan agreed last week.

In case the truce collapses, the European Union said it was ready to impose a new round of sanctions against Russia, which might even come into force today.

If they do, Russian Prime Minister Dmitry Medvedev said that Moscow is prepared to respond "asymmetrically" to new sanctions over the Ukraine crisis, possibly targeting flights over Russia.

For the Russian leader, "sanctions do not help to establish peace in Ukraine." Instead, "the security system in the world could be undermined."

"I hope," he added, "that our Western partners do not want this and there are no crazy people among those who take the decisions".

• russia
• ukraine
• separatists
• war
• ceasefire
• truce