The intruder, whose motivation was not immediately known, was detained by station security staff and handed over to police. The victim, Tatyana Felgengauer, has been hospitalised but her life is not in danger, the station said.
Ekho Moskvy is owned by a media holding ultimately controlled by state-owned gas giant Gazprom. It does however, give air time to journalists and commentators who are fiercely critical of the Kremlin and its allies.
One of the station's regular broadcasters, Yulia Latynina, said earlier this year she had been forced to flee Russia after a series of attacks, including the torching of her car.
A spokesman for the Russian Prosecutor-General's office, Alexander Kurennoi, said on Facebook the attack was an outrageous act. She said he had assured the station's managers that the situation would be kept under control.
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