Ukrainian officials said their forces advanced to the outskirts of a key town north of Donetsk on Saturday as they try to retake the stronghold held for months by pro-Russia rebels.

The move comes as Ukrainian forces appear to have gained some momentum recently by retaking control of territory from the rebels. But Russia also appears to becoming more involved in the fighting, with the U.S. and Ukraine accusing Moscow of moving heavily artillery across the border to the rebels.

Ukrainian national security spokesman Andriy Lysenko said Ukrainian forces were outside Horlikva, just north of the regional centre of Donetsk.

Once they can take Horlivka, "the direct route is open for the forces of the anti-terrorist operation to the capital of the Donbass region — the city of Donetsk," Lysenko said. "The approaches to Donetsk are being blocked so that the terrorists do not get the chance to receive ammunition, reinforcements or equipment."

Donetsk, a city of about 1 million people, is a major centre of the separatist uprising that has battled Ukrainian government forces for five months.

An Associated Press reporter found the highway north of Donetsk blocked by rebels and heard the sound of artillery to the north. Explosions were heard in the direction of the town's airport, on the northwest edge of the city, an area frequently contested by Ukrainian forces and rebels. Black smoke rose from the direction of Yakovlikva, a northern suburb of Donetsk.

About 60 kilometres to the east, the site where Malaysia Airlines Flight 17 was shot down was still eerily empty except for the parents of one of the 298 people killed in the July 17 disaster. A full-fledged investigation still hasn't started because of the security risks posed by the nearby fighting.

But Jerzy Dyczynski and Angela Rudhart-Dyczynski, parents of 25-year-old Fatima, travelled from their home in Perth, Australia to honour their daughter. They crossed territory held by pro-Russian rebels to reach the wreckage-strewn fields outside the village of Hrabove, where they sat together on part of the debris, his arm around her shoulder.

Fatima "was for peace. She will be forever for peace," her father said.

U.S. and Ukrainian officials say the plane was shot down by a missile from rebel territory, most likely by mistake.

Two military cargo planes, one Dutch and the other Australian, also flew 38 more coffins carrying victims to the Netherlands for identification and investigation.

Last coffins

Later, the Dutch government said the first formal identification of a victim had taken place. The name and sex of the victim, a Dutch national, were not released.

The planes took off Saturday from Kharkiv, a government-controlled city where the bodies have been brought from the wreckage site in territory held by pro-Russian separatists fighting the Ukrainian government. They landed later in the afternoon in Eindhoven, where the coffins were transferred to a fleet of hearses in a solemn ceremony.

Russian President Vladimir Putin has said sanctions will hurt bilateral ties between nations. (Alexei Nikolskyi/RIA Novosti/Reuters)

Officials said the flights took the last of the 227 coffins containing victims that had been brought to Kharkiv by refrigerated train. Officials say the exact number of people held in the coffins is still to be determined by forensic experts in the Netherlands, where Ukraine agreed to send the bodies. International observers have said there are still remains at the wreckage site. Access has been limited due to rebel interference and security concerns.

The disaster sparked hopes in the West that Russia would scale back its involvement in the uprising in Ukraine's east, but nine days later the opposite seems to be the case.

Russia launched artillery attacks from its soil into Ukraine on Friday, while the United States said it has seen powerful rocket systems moving closer to the Ukraine border.

Those accusations sparked a strong denial from Moscow, which accuses the U.S. of a smear campaign.

'Unrelenting campaign of slander'

The Russian Foreign Ministry accused the United States on Saturday of conducting "an unrelenting campaign of slander against Russia, ever more relying on open lies."

The ministry took particular issue with comments Friday by White House spokesman Josh Earnest, who said Washington regards Moscow as involved in the shooting down of the airliner because it allegedly has supplied missile systems to the rebels and trained them on how to use them.

The ministry complained that these allegations have not been backed up with public evidence and it sneered at Earnest for saying they are supported by claims on social media.

"In other words, the Washington regime is basing its contentions on anti-Russian speculation gathered from the Internet that does not correspond to reality," it said.

Men remove debris from their damaged house in the city of Lisichansk, Luhansk region, eastern Ukraine Saturday. (/Dmitry LovetskyThe Associated Press)

Russia also lashed out at the latest round of Ukraine-related sanctions imposed by the European Union, saying they endanger the fight against international terrorism.

The EU sanctions, announced on Friday, impose travel bans and asset freezes on 15 people, including the head of Russia's Federal Security Service and the head of the agency's department overseeing international operations and intelligence. Four members of Russia's national security council are also on the list.

The Foreign Ministry said the sanctions show the EU is taking "a complete turn away from joint work with Russia on international and regional security, including the fight against the spread of weapons of mass destruction, terrorism (and) organized crime."

"We are sure the decisions will be greeted enthusiastically by international terrorists," the ministry said.

Meanwhile, CNN reported that a Ukrainian freelancer who had been detained by separatists was freed on Saturday. The journalist, Anton Skiba, was seized Tuesday in the rebel-controlled city of Donetsk when he and other members of a TV crew returned to a hotel after working at the site of the downed Malaysian airliner.

A day earlier, the anti-Kremlin newspaper Novaya Gazeta ran a full front-page photo of a cortege of hearses with the headline in Dutch and Russian saying: "Forgive us, Holland."