Yatsenyuk had almost ended up his weekly questions session when a lawmaker from President Petro Poroshenko's faction, Oleg Barna, came up to him and handed him a bunch of red roses, an AFP correspondent reported from the scene.
Barna - a fierce opponent of Yatsenyuk who has campaigned for him to resign - then grabbed Yatsenyuk by the waist from behind and forced him out of the rostrum.
This prompted dozens of male MPs to rush to intervene and they began scuffling and trading blows.
Nobody was reportedly injured in the brief fight between lawmakers of pro-Poroshenko's faction and Yatsenyuk supporters.
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Such brawls are not rare in Ukraine's 450-seat unicameral parliament, highlighting the fragile nature of Ukraine's pro- Western coalition made up of Poroshenko's and Yatsenyuk's factions and two smaller groups.
"This is shameful for our country," added Viktoria Syumar, a lawmaker from Yatsenyuk's Narodny Front faction.
The leader of Poroshenko parliamentary bloc, Yuriy Lutsenko, immediately apologised for the incident, promising that his colleague Barna would be "reprimanded" for this "unacceptable act".
The year-old pro-Western parliamentary coalition is struggling to overcome internal splits as it struggles with the economic crisis and the deadly conflict with pro-Russian rebels in the eastern Ukraine that has already claimed more than 9,000 lives.