Ukraine's army has said it has retaken a town on the outskirts of the main rebel stronghold of Donetsk, and intercepted another convoy of vehicles crossing over from Russia.
Government forces said in a statement on Wednesday that they had seized control of Avdiyivka, a town of about 40,000 about a dozen kilometres north of Donetsk, as Ukraine tightened its grip around the key rebel bastion.
The Ukrainian government said on its website that 19 people had died in the fighting in the past 24 hours, with 31 people injured.
Elsewhere, clashes continued around the crash site of Malaysia Airlines Flight 17, with government forces saying they were conducting a "mopping up" operation in the town of Ilovaysk, about 40km west of the site.
International observers announced they had turned back from another attempt to reach the crash site after discussions with the rebels, AP news agency reported.
Safety concerns and hindrance from the separatists who control the area have kept the OSCE investigation team away from the scene, causing foreign governments whose citizens died in the July 17 crash to complain the site is not secured and some human remains have not been recovered.
Government security spokesman Andriy Lysenko added to those concerns on Wednesday by saying separatists "have mined the approaches to this area", AP reported.
ANALYSIS: OSCE in Russia
The latest advances in Donetsk come as government troops attempt to push on with an offensive that has seen them reclaim several key towns in the past few weeks, and could see them cut alleged supply routes from Russia to rebels camped out in Donetsk.
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The military said that they had repulsed tank fire to destroy a convoy of vehicles that crossed the Russian border early on Wednesday morning and that troops at the key Dovzhansky frontier post had been fired at from Russia.
Fighting also raged in the second rebel stronghold of Luhansk with local authorities saying that one civilian was killed and 10 injured in clashes over the past 24 hours.
A defiant Russia dismissed on Wednesday the unprecedented Western sanctions over Ukraine after Brussels and Washington unveiled the toughest punitive measures against the Kremlin since the Cold War.
The third round of US and EU sanctions aims to force Russia to change tack and halt its support of separatists in Ukraine by targeting its vital financial, arms, and energy sectors.
But Russia's first deputy prime minister, Igor Shuvalov, made light of the restrictions, also designed to hit the oligarchs in Russian President Vladimir Putin's inner circle.
"And what about the sanctions? In for a penny, in for a pound," he said.
Meanwhile, Russia's second-largest bank, VTB, called the sanctions "unjust" and "politically motivated".
The US put sanctions on VTB, Bank of Moscow, and Russian Agriculture Bank on Tuesday over Russia's support for the rebels in Ukraine, expanding the list of Russian banks subject to US sanctions to almost all banks with more than 50 percent of state ownership, except for Sberbank.
Russia denies supporting the rebels fighting Ukrainian forces in eastern Ukraine.
"We consider the decision to be politically motivated, unjust, legally dubious and likely to cause economic harm to all sides," VTB said in a statement.