West Ham's Israeli international Yossi Benayoun has spoke of his embarrassment at hearing anti-Semitic abuse by some of the club's fans towards Tottenham's supporters.
The Football Association has launched an investigation into reports of the abuse, while West Ham reacted by banning for life one of two fans cautioned by police at the match at White Hart Lane on Sunday. Some Hammers fans appeared to mock both the gassing of Jews in the Holocaust and the knife attack on a Spurs fan before Tottenham's game in Rome last week.
Benayoun said on Twitter: "I have a great relationship with the West Ham United supporters, from my first spell at the club and again now I am back on loan here. This (is) why I was very disappointed to hear some of the songs yesterday and it was embarrassing."
West Ham supporters sang "Viva Lazio", "Can we stab you every week?" and hissed on several occasions, apparently mocking the mass execution of Jews during the Second World War.
Police confirmed that two West Ham supporters were formally cautioned by officers after singing anti-Semitic chants during Sunday's match. The pair of fans were arrested during the game and accepted the police cautions, Scotland Yard said.
One of those was a Hammers season ticket holder who has since been banned for life by the club. A club statement said: "West Ham will take the strongest possible action against any of their supporters, including enforcing life bans from the club, that are found guilty of behaviour which is categorically not condoned by West Ham."
The chants from a section of West Ham supporters have been reported to the police by the Society of Black Lawyers.
Tottenham will be submitting video evidence as part of their report to the FA, and a club spokesman said: "We are currently compiling a full report for the Football Association and shall be submitting this with all our evidence including relevant CCTV footage."
The Community Security Trust (CST), a charity that monitors anti-semitism, said it has received complaints from people in the Jewish community following the Spurs match, including from people who were at the game.
CST spokesman Mark Gardner said: "The days of English football crowds making massed monkey noises are thankfully gone, but massed anti-Semitic chanting about Hitler and gassing was clearly heard from a loud section of West Ham fans. We have heard such abuse against Spurs before and it risks seriously compromising the work against racism at all levels of the game."