[This post was accurate at the time, but is sadly out of date. Islamic State has toppled, sledgehammered and jackhammered (drilled out) artefacts in Mosul Museum and at Nineveh.]
24 News (@24news__) reported in Arabic, ‘Iraq: “Daash” gunmen seize Nineveh Museum, and they destroyed ancient masterpieces, including the rare Assyrian winged bull [العراق : مسلحو “داعش” يستولون على متحف نينوى ويقومون بتكسير التحف منها تحفة الثور الاشوري المجنح النادرة]’. Coptic Nationalism (@DioscorusBoles) repeated the news in English, ‘ISIS destroys archaeological monuments at Mosul (Nineveh) Museum, including the famous winged Assyrian bull’ (and others copied-and-pasted or modified it).
However, as Christopher Carlson (@C_Perspective_) observed, news and social media were [not] sharing [an image from Mosul]…. ‘The one in Mosul wasn’t in as good condition.’ Update (29th June 2014): Jastrow has kindly clarified that the šēdu/shedu/lamassu is ‘one of the reliefs from Dur-Sharrukin now at the Louvre, cf‘. (Making the original report even less reliable, there were two winged lions (not bulls) from Nimrud in Mosul Museum.) I haven’t been able to find any photos of artefacts from Nineveh Museum that have been destroyed by ISIS. I’ve searched the Arabic-language “news” but haven’t been able to find any report other than the original headline.
Moreover, the claims of the destruction of the winged bull and other artefacts were first spread on the 21st of June. Yet, on the 23rd, the British Institute for the Study of Iraq (BISI) issued a statement that did not mention any destruction at that (or any other) museum; and the Council Chair, Eleanor Robson (@Eleanor_Robson), explicitly stated that ‘all’ of the museums in the affected areas had been ‘reported safe so far’. There is no evidence that the Assyrian winged bull or Mosul/Nineveh Museum’s other artefacts have been destroyed.