The remains of the last nine victims of flight MH17 may never be recovered from the Ukrainian battlefield where their plane was downed four months ago, the Dutch foreign minister said Saturday, as fighting rumbled on in the east of the country.

Foreign Minister Bert Koenders made the grim assessment in the city of Kharkiv, where he attended a memorial service for five more sets of human remains collected from the site of the disaster and flown to The Netherlands.

Another ceremony attended by some 1,600 friends and relatives was planned to take place in The Netherlands on Monday.

"We cannot say at this moment in any certain way... at what moment, and even if, we can recover the last nine" victims, he said of the air crash that killed all 298 on board, including 193 Dutch.

The shooting down of the Malaysia Airlines Boeing 777 on July 17 was one of the worst tragedies of a war in which an estimated 4,000 people have died. So far, the remains of 289 of those victims have been identified.

Ukraine and the West blame Russian-backed separatist fighters using surface-to-air missiles for the catastrophe, while Moscow has pointed the finger at Kiev's forces, in an incident that galvanised international shock over the chaos in a country bordering the European Union.

More bloodshed

Ukraine reported more bloody fighting, with eight of its soldiers killed in the last 24 hours, as Moscow denied claims it had sent tanks across the border.

Ukraine's military said one of those killed was a paratrooper shot by a sniper in Donetsk international airport, where government forces are defending a pocket of territory near the biggest rebel-held city.

Seventeen other soldiers were wounded in shelling of government positions around the conflict zone, according to updates from the military.

The fighting rumbled on in the industrial east despite a two-month-old ceasefire deal that has halted significant offensives, but failed to stop shelling at strategic flashpoints.

Donetsk's city hall and Ukrainian authorities reported the wounding of three civilians.

After a brief morning calm, the sound of artillery explosions started up again, mostly near the airport, and continued relentlessly into the night, an AFP journalist said.

Two tanks and two armoured fighting vehicles could be seen on the outskirts of the city, while rebels were digging trenches.

"These are our armoured vehicles changing position to escape the firing by the Ukrainians," said Zoya, a local resident who was coming to check on her house which she'd been forced to abandon for a safer location with friends elsewhere in the city.

Not everyone in the neighbourhood had that luxury.

"Where could I go? I have nowhere to go, no one who can give me shelter. Also, this is where my house is," said Vladimir, 78, while sawing firewood.

"Whatever happens will happen," the former miner said. "If I have to die under the bombs, then that's the way it's meant to be."

Claim of tanks

Russia, which annexed Ukraine's Crimea region in March and lends close political and humanitarian support to the separatist areas in the east, denied the latest Ukrainian allegation that it was dispatching regular troops to join the fighting.

Ukraine's military made headlines around the world on Friday with the claim that columns of hardware, including 32 tanks, had poured across the border which is under the control of Russia and the pro-Russian rebels.

However, Foreign Minister Sergei Lavrov laughed off the allegation after US State Department spokeswoman Jen Psaki said she had no "independent confirmation" of the report.

"If Psaki doesn't have it, I don't," Lavrov told journalists with a chuckle in Beijing, where he met his US counterpart John Kerry ahead of an APEC summit.

Diplomatic activity

The conflict has sent relations between Western backers of Ukraine and Russia to their lowest level in decades.

"The world is on the brink of a new Cold War. Some are even saying that it has already begun," the last Soviet leader, Mikhail Gorbachev, said at an event marking the 25th anniversary of the fall of the Berlin Wall.

In an interview with Switzerland's RTS radio and TV network, due to be aired on Sunday, Gorbachev said: "One sees new walls. In Ukraine, it's an enormous ditch that they want to dig."

Russia's economy is suffering from European Union and US sanctions imposed in response to Moscow's support for the separatists. With Russia welcoming last week's rebel elections, which were billed as boosting the separatists' claim to independence, sanctions look set to remain in place -- and possibly be reinforced.

"We see no reason to lift any sanctions," Koenders said in Kiev, calling the rebel elections "illegal".

A flurry of diplomatic activity is approaching, with the APEC summit in China and a Group of 20 meeting in Australia next week, where President Vladimir Putin will have the chance to put his case before world leaders.

Speaking in Beijing, Lavrov appeared to soften Russia's position, saying that US involvement in attempts to resolve the crisis would be a "step in the right direction".

But in comments marking the Berlin Wall anniversary, US President Barack Obama said, "As Russia’s actions against Ukraine remind us, we have more work to do to fully realise our shared vision of a Europe that is whole, free and at peace."