Fighting around two flashpoint cities in eastern Ukraine has rattled a tenuous truce between government troops and pro-Russian rebels less than 48 hours after it came into force.

Insurgent militias bombarded a government-held checkpoint on the eastern edge of the port city of Mariupol on Sunday, local officials said, killing one woman and triggering panic among residents.

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Artillery fire was also heard near the main rebel stronghold of Donetsk, AFP correspondents said, with the Ukrainian government accusing separatist gunmen of trying to attack the city’s airport.

The violence erupted just hours after a phone call between Ukraine’s President Petro Poroshenko and his Russian counterpart Vladimir Putin, who agreed that the ceasefire was “generally being observed”.

EU leaders plan to put further pressure on Russia over its alleged support for the insurgents by approving fresh sanctions on Monday on its defence and oil companies, although the bloc’s President Herman Van Rompuy said these steps could be reviewed “if the ceasefire is durable, and/or if the peace talks start”.

The 12-point pact signed in Minsk on Friday was the first to win the backing of both Kiev and Moscow after five months of warfare that set off the deepest crisis in East-West relations for a generation.

But it delays difficult decisions about the status of the two rebel-run regions of Donetsk and Lugansk until later negotiations, which one separatist leader said may begin in about a week.

The peace plan was drawn up after the rebels – reportedly backed by Russian troops and firepower – launched a lightning counter-offensive in late August that dramatically reversed recent gains by the Ukrainian army and set alarm bells ringing over Moscow’s territorial ambitions.

Both sides had accused the other of violating the truce within hours of its signing, raising fears it could go the way of a unilateral ceasefire called by Kiev in June that collapsed within days.