Ukraine Is Launching an Offensive to Retake Donetsk

The Ukrainian military launched an attack on Saturday in an effort to retake the rebel stronghold of Donetsk.

Forces have reached the border of the town of Horlivka, Ukrainian national security spokesman Andriy Lysenko told the Associated Press, and amassed there in the area north of Donetsk, which is at the heart of a bloody separatist uprising that has now plagued the country for months.

"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 army is also advancing from the south and has sealed off a road leading from the port city of Mariupol, where it has assembled some 6 miles from Donetsk, Reuters reported.

Loud explosions were heard in and around Donetsk today as Ukrainian troops pushed forward with their campaign.

"Last night was terrible. I was woken up at 3AM by the explosions. The walls shook, the windows shook," one local resident, Marina, told Reuters. "There was shooting all over the city. And it still goes on."

Donestsk, a city of roughly 1 million, lies approximately 35 miles from the open field where Malaysian Airlines Flight 17 was shot down by pro-Russia rebels near the Russian border on July 17.

The unsecured site where the plane crash-landed, killing all 298 civilians on board, has been the scene of a limited investigation conducted amid reports that rebels have tampered with evidence and severely restricted the movement of foreign monitors.

It's time to assign blame for everything that happened in Ukraine. Read more here.

Speaking on July 21, Obama said that “Russian-backed separatists who control the area continue to block the investigation” of the crash, and called on Russian President Vladimir Putin to “get serious about trying to resolve hostilities within Ukraine.”

Alexander Borodai, Prime Minister of the self-proclaimed Donetsk People's Republic militia group, denied any wrongdoing, despite accounts that rebels have been snatching plane fragments and carting away charred bodies and parts from the unsecured site.

The US has implicated Russia in the downing of the plane, saying that the country provided the surface-to-air missile equipment and trained the rebels in Ukraine that perhaps mistakenly targeted the airliner.

Moscow has routinely denied the claims.

The incident sparked international outrage and promoted hopes that Russia would pull back its military involvement with the rebels, but that optimism was short-held, with Russia making moves to bolster its support of the uprising both directly and indirectly.

On Friday, Russia fired five rounds of heavy artillery into eastern Ukraine from across the border, according to Lysenko.

US officials backed up the claims, saying, "For the last several days Russian forces using Russian artillery from Russian soil have conducted attacks against Ukrainian military positions in Ukraine."

"This is unquestionably an escalation from a military perspective," Pentagon spokesman Col. Steve Warren said on Friday.

The US and Ukraine both say they also have proof that Russia was planning to deliver even more powerful multiple rocket launchers to supporters in Ukraine in coming days.

Further east, in the rebel-held city of Luhansk, at least 19 civilians were killed in fighting overnight, according to separatists.

Who's Who in the Donetsk People's Republic. Read more here.

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Follow Liz Fields on Twitter: @lianzifields