KYIV (AFP) - Ukraine on Monday (Feb 21) firmly denied Russian claims that Russian forces had killed five Ukrainian "saboteurs" who allegedly crossed the border to stage an attack.

Foreign Minister Dmytro Kuleba denied a string of claims issued by Russian officials throughout a tense day that has intensified fears that the Kremlin is paving the way for an invasion of Ukraine.

Russian officials had earlier also said that a Ukrainian shell had destroyed a border facility used by Russia's Federal Security Service.

"No, Ukraine did NOT: attack Donetsk or Lugansk, send saboteurs or APCs (armoured personnel carriers) over the Russian border, shell Russian territory, shell Russian border crossing, conduct acts of sabotage," Mr Kuleba said in an English-language tweet.

"Ukraine also does NOT plan any such actions. Russia, stop your fake-producing factory now."