At least five people were killed Friday in fighting near Ukraine’s eastern hub of Donetsk two days before a presidential election undermined by an upsurge in attacks by pro-Russian separatists.

The latest bloodshed on the heels of the deaths of 18 soldiers on Thursday in the eastern rustbelt near Russia underscores the trouble the interim leaders have in making sure they can pull off a safe and well-attended vote Sunday.

Interim president Oleksandr Turchynov appealed to voters to come out and show their support for a free and democratic Ukraine in the face of an insurgency he and Western leaders accuse Russia of orchestrating.

“We will never again stand being denied freedom and independence or seeing our Ukraine being turned into a part of a post-Soviet empire,” he said in a brief nationally-televised address.

Friday’s fighting pitted a volunteer force attached to the Ukrainian army against militants armed with heavy machine guns and backed by at least one armoured vehicle.

An AFP photographer saw five bodies near the village of Karlivka northwest of Donetsk.

Four of the dead appeared to be rebels and one man with a swastika tattoo seemed to have fought for the so-called Donbass volunteer battalion that has backed government troops since the fighting first broke out more than a month ago.

Battalion commander Semyon Semenchenko described in a rapid-fire series of Facebook posts how his unit was ambushed and then surrounded after taking refuge in a vacant building along the main road.

“Exactly half our unit has been wounded. Many have lost lots of blood,” he said.

Semenchenko later appealed on the rebels “to agree to a truce in exchange for a prisoner swap.”

Eighteen soldiers were killed in separate attacks in Donetsk and the neighbouring region of Lugansk on Thursday in the heaviest loss for the military since launching what it calls an “anti-terrorist” operation against the rebels in mid-April.

The West has threatened Russia with painful sanctions against entire sectors of its troubled economy should it be deemed to have disrupted an election that is almost certain to bring a new pro-Western leader to power.

German Chancellor Angela Merkel called on Russian President Vladimir Putin to accept the assessment of about 1000 observers from the Organisation for Security and Cooperation in Europe who are monitoring the election throughout the country of 46 million people.

In the face of the Western threats, Moscow has ordered the withdrawal of some 40,000 troops it has massed along its western neighbour’s border since seizing Crimea in reprisal for the February popular overthrow of a Kremlin-backed regime.

But Russian Foreign Minister Sergei Lavrov accused the West of trying to contain his country and urged Moscow’s Cold War-era foe to learn “the right lessons” from Europe’s worst security crisis in decades.

Kiev media are describing the election as the most important since Ukraine’s independence in 1991 because it gives people a chance to unite behind a legitimate leader after months of unrest that have exposed a deep cultural divide between its Russian and Ukrainian speakers.

But Kiev’s interim leaders admit they will have a tough time making sure polling goes smoothly in restive eastern provinces that are home to nearly seven million Ukrainians and represent the country’s vital coal and steel belt.