Ukraine conflict: Russia accuses US of 'smear campaign'
Russia has accused the US of launching a "smear campaign" over its alleged involvement in the conflict in Ukraine.
The foreign ministry in Moscow said on Friday it rejects "unfounded public insinuations" from the US government.
But the Pentagon says it believes the movement of Russian heavy-calibre artillery systems across the border into Ukraine is "imminent."
The row comes as more bodies of victims from flight MH17, which crashed in Ukraine, arrived in the Netherlands.
Separatist rebels in eastern Ukraine have been accused of shooting down the Malaysia Airlines plane.
The US says it believes rebels shot down the passenger jet with a Russian-provided SA-11 Buk surface-to-air missile, probably by mistake.
Russia has frequently denied sending heavy weapons into Ukraine but rebel leaders have given conflicting accounts of whether they had control of a Buk launcher at the time the plane was downed.
The Pentagon said on Friday that it had evidence to suggest Russia is preparing to transfer more rocket launcher systems to the rebels.
"We have indications that the Russians intend to supply heavier and more sophisticated multiple-launch rocket systems in the very near future," Col Steve Warren, a Pentagon spokesman, said on Friday.
On Thursday, a US state department spokesperson said there was also evidence Russian troops were firing on Ukrainian soldiers from within Russia.
But in a statement, Russia's foreign ministry said the US was pushing "anti-Russian cliches" to protect their allies in Kiev by obscuring the "real reasons for events in Ukraine".
The BBC's Sarah Rainsford in Moscow says that amid all the accusations of war-mongering, it seems Russia is keen to stress that so far, it has actually shown restraint.
Meanwhile, the EU has formally announced that it is strengthening sanctions against Russia, adding "15 further persons and 18 entities" to an asset freeze and a visa ban.
A statement released on Friday said that those targeted are "responsible for action against Ukraine's territorial integrity".
The Russian officials targeted include Federal Security Service head Alexander Bortnikov and foreign intelligence head Mikhail Fradkov.
The fighting in eastern Ukraine erupted in April and is believed to have claimed more than 1,000 lives.
On Friday, the Ukrainian army said its troops had come under artillery fire from the Russian side of the border overnight and were attacked by rebels in several areas in the east.
The US has repeatedly accused Russia of fuelling separatist sentiment in eastern Ukraine and has toughened its rhetoric since flight MH17 was downed.
'Spy or a big one?'
Ukraine officials published the latest in a series of audio recordings on Friday that appears to be a conversation between rebels, minutes before MH17 crashed.
In the recording, which has not been independently verified, a rebel tells a commander that a "bird had flown" in his direction.
When the commander asks if it was a "spy or a big one?" the rebel says that he cannot tell because it is flying too high.
All 298 people on board the flight died in the crash on 17 July, including 193 Dutch citizens, 43 Malaysians and 27 Australians.
About 200 bodies were recovered from the crash site in eastern Ukraine and are being flown to the Netherlands, where forensic experts are working on identifying them.
The Dutch and Australian foreign ministers are negotiating with Ukrainian officials in Kiev to send police to the crash site, which is controlled by the rebels.
They hope that such a deployment would allow experts, who have faced difficulties gaining access to the site, to proceed with the investigation amid continuing fighting in the region.