The Irish FA has contacted European governing body Uefa after travelling Northern Ireland fans complained of "shameful and totally unacceptable treatment" from authorities while attending Sunday night's 1-0 Nations League defeat in Bulgaria.A statement from the Amalgamation of Northern Ireland Supporters Clubs (AONISC) complained that fans had been denied access to water and toilets while being held inside the Hristo Botev Stadium following the game.In a separate incident, one Northern Ireland supporter required hospital treatment after being involved in what was described as a violent attack while walking back into the city centre following the game.An Irish FA spokesperson said: "On arrival back in Belfast today we have engaged with UEFA at a senior level to indicate that our fans do not have the history or profile which suggests they deserve the type of treatment that has been reported."We expect an update in due course and want to take this opportunity to thank our fans for their continued support."In its own statement, the AONISC said: "We witnessed the shameful and totally unacceptable treatment of our fans in Plovdiv last night."Locking us inside our sector not only denied Northern Ireland fans access to the basic rights of water and toilet facilities, it also created a serious safety issue."We contacted Irish FA staff, who in turn spoke to the UEFA delegate, and eventually, the gates were opened."The statement added: "The treatment of Northern Ireland fans, who were well behaved as ever, was in stark contrast to the lack of stewarding of home fans, some of whom repeatedly threw missiles into our sector until midway through the second half."We found the attitude of the police in Plovdiv more difficult as the day