Ukraine's Russian-held Nova Kakhovka dam was damaged in shelling by Ukrainian forces, Russian news agencies reported on Sunday, citing emergency services.
Russian state-owned news agency TASS quoted a representative of the emergency services as saying that a rocket launched by a U.S.-made HIMARS missile system had hit the dam's lock and caused damaged. The official quoted said it was an "attempt to create the conditions for a humanitarian catastrophe" by breaching the dam.
The reports provided no evidence to support the allegation, which could not be immediately verified by Reuters.
The vast Nova Kakhovka dam, which blocks the Dnipro river upstream of Kherson where Ukrainian forces have been making advances, has taken on vital strategic significance in recent weeks.
Both Russia and Ukraine have since October repeatedly accused each of planning to breach the dam using explosives, in a move that would flood much of the area downstream in what would likely cause major destruction around Kherson city.
(Reporting by Reuters, Editing by William Maclean and Hugh Lawson)