Update: according to WaPo reported Mustafa Salim the Iraqi 7th division commander has "completely denied" any attack took place:
I just called the Iraqi army 7th division commander who is based there, he completely denied it— Mustafa Salim (@Mustafa_salimb) January 3, 2020
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All day there was speculation if, when and how Iran would respond to the assassination of Soleimani, and moments ago we may have gotten the answer when NYT reporter Farnaz Fassihi tweeted that there are "Unconfirmed reports of ballistic missiles hitting largest US military base Ain Al-Assad in #Iraq & massive explosions, via IRGC Telegram channels"
Breaking: Unconfirmed reports of ballistic missiles hitting largest US military base Ain Al-Assad in #Iraq & massive explosions, via IRGC Telegram channels.— Farnaz Fassihi (@farnazfassihi) January 3, 2020
A similar report came out from reporter Sina Toossi who notes that an Iraqi Twitter has posted a picture of the alleged missile attack on al-Ain base, and notes that Iranian outlet Mehr has also reported massive explosions at the Ain al-Assad military base in Iraq’s Anbar province, the largest US military base in the country.
Iraqi Twitter user posts picture of alleged missile attack on al-Ain base. Not confirmed. pic.twitter.com/r78qZfVktQ— Sina Toossi (@SinaToossi) January 3, 2020
Others however remain skeptical, speculating the report is just Iranian psyops:
False alarm about Iran bombing Ain Assad air base in Iraq. Iran begins with psychological ops.@SSanbeer این میگه ایران قدم اولش رو با تنش روانی آغاز کرده و این داستان عین الاسد فیک و دروغ هست.#عین_الاسد— Daniel Topaloglu (@DanielTopaloglu) January 3, 2020
While the report remains unconfirmed, stocks reacted instantly, sliding sharply if rebounding modestly.