Is sex by couples married under nikah mut'ah interpreted as zina in Sunni Islam, and punishable under Sharia?

> Nikah al-mut'ah is a type of marriage permitted in Twelver Shia Islam, where the duration of the marriage and the mahr must be specified and agreed upon in advance. ... > > Sunni Muslims, and within Shia Islam, Zaidi Shias, Ismaili Shias, and Dawoodi Bohras do not practice Nikah mut'ah. -- Wikipedia The above sentence indicates that Sunni Muslims (and others) don't perform nikah mut'ah weddings. I'm not sure if it implies nikah mut'ah marriages (performed where they are considered valid) are recognized in Sunni Islam. If nikah mut'ah is not recognized, then sex between such couples would logically amount to zina (fornication), which is punishable under Sharia. **Question**: Is sex by couples married under nikah mut'ah interpreted as zina in Sunni Islam, and punishable under Sharia? An answer by Zohal and a comment by Aboudi for https://islam.stackexchange.com/q/17732/17163 expresses this viewpoint, although these weren't backed up by an authoritative reference (so I don't know if they're just expressing a personal opinion).