More from U.S. State Department spokeswoman Jen Psaki at a press briefing in Washington, D.C.:
"There were reports of additional columns of Russian tanks, multiple rocket launchers, and armored vehicles pushing toward communities in southeastern Ukraine. We've also seen reports of separatists shelling residential areas in a costal town between the border and Mariupol. We have seen reports of heavy fighting and shelling near the city and airport in Donetsk. These incursions indicate a Russian directed counteroffensive is likely under way in Donetsk and Luhansk."
"We are also concerned by the Russian government's unwillingness to tell the truth even as its soldiers are found 30 miles [48 kilometers] inside Ukraine. Russia is sending its young men into Ukraine but are not telling them where they are going or telling their parents what they are doing."
From our news desk:
Kremlin spokesman Dmitry Peskov said that claims about an upsurge in Russian military activity on the border with Ukraine have “nothing to do with the reality.”
Peskov added that Russia is ready to send a second humanitarian aid convoy to eastern Ukraine "even tomorrow."
An earlier convoy entered Ukrainian territory last week without Kyiv's permission, raising tensions between the West and Moscow.
Peskov also said Russia is and will be a reliable supplier of natural gas to Europe, following warnings from Kyiv that Moscow could cut off fuel to the continent this winter.
"We hope that Ukraine in turn will guarantee unhindered transit," he added.
This ends our live-blogging for August 27. Be sure to check back tomorrow for our continuing coverage of the crisis in Ukraine.
Good morning. Major developments overnight:
-- U.S. State Department spokeswoman Jen Psaki says reports from eastern and southeastern Ukraine "indicate that a Russian-directed counteroffensive is likely under way" against government forces in Ukraine's Donetsk and Luhansk regions.
-- Germany has demanded an explanation from Moscow amid reports of the presence of Russian soldiers in eastern Ukraine. In a phone call with Russian President Vladimir Putin on August 27, German Chancellor Angela Merkel said the reports “must be explained," her spokesperson said.
More in our latest news wrap.