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 center of Donetsk.
"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.
Donetsk, a city of about 1 million people, is a major center 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 35 miles (60 kilometers) 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 accident. Nine days after the accident, a full-fledged investigation still hasn't started due to the security risks posed by the nearby fighting.
But Jerzy Dyczynski and Angela Rudhart-Dyczynski, parents of 25-year-old Fatima, crossed territory held by pro-Russian rebels to reach the wreckage-strewn fields outside the village of Hrabove to visit the place of their daughter's death.
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 more cargo planes also flew 38 more coffins carrying victims to a forensic center in the Netherlands for identification and investigation.
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.
Officials said the flights took the last of the 227 coffins containing victims that have 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 has 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.
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 contentions have not been backed up with public evidence and it sneered at Earnest for saying the allegations are backed up 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.
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.