Maria Stolyarova worked as a contract producer with a highly-rated Russian-language weekly news show on Inter -- a channel that has often been accused of tacitly backing the Kremlin and opposing Ukraine's pro-Western leadership.
Inter is owned by a top aide to Ukraine's ousted Russian-backed president and has previously faced parliamentary calls to have its license removed.
"Russian journalist Maria Stolyarova received a one-way ticket (out of the country) and left the territory of our state under the supervision of security service personnel," Ukrainian Security Service spokeswoman Olena Gitlyanska wrote on Facebook.
Stolyarova is a Russian citizen who worked with a pro-Kremlin Moscow TV channel before joining a Ukrainian television production company that Inter hired for its weekly news roundup.
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That company fired Stolyarova today after a firestorm erupted over a series of pictures she posted on Facebook with camouflage-clad armed pro-Russian fighters that she described as "my beloved guys".
The outrage grew only stronger when activists found a Facebook post from March 2014 in which she called for the deployment of Russian troops in Ukraine so that they could reverse the former Soviet republic's new pro-European course.
The company contracted by Inter said it sacked Stolyarova over an episode Sunday in which she was heard swearing on air while the channel was showing pictures of mourners honouring victims of the February 2014 police shooting of pro-EU protesters.
Sunday's incident prompted many to try and find out more about Stolyarova by digging through her Facebook account.
Stolyarova said yesterday that the expletive that accidentally went on air was aimed at the programme's presenter and in no way expressed her opinion about the more than 100 that died.