Liverpool striker Luis Suarez on Sunday apologised for biting Chelsea defender Branislav Ivanovic during the sides' 2-2 Premier League draw at Anfield.
The incident occurred mid-way through the second half, with Liverpool trailing 2-1 following a tussle in the penalty area.
"I'm sad for what happened this afternoon, I apologize (to) Ivanovic and all (the) football world for my inexcusable behaviour. I'm so sorry about it!!," the controversial Uruguayan said on his Twitter account.
"I apologise also to my manager, playing colleagues and everyone at Liverpool Football Club for letting them down," he added.
Referee Kevin Friend did not appear to see the incident and took no action, despite Ivanovic attempting to show him the bite-marks on his arm.
Suarez had earlier been booked for a handball that gifted Chelsea the penalty from which Eden Hazard put the visitors 2-1 up, but he finished the game by heading in a dramatic equaliser in the seventh minute of injury time.
Liverpool managing director Ian Ayre commented: "Luis has made an unreserved apology for his actions today.
"His behaviour is not befitting of any player wearing a Liverpool shirt and Luis is aware that he has let himself and everyone associated with the club down. We will deal with the matter internally and await any action from the FA."
Reds' coach Brendan Rodgers said on the club website: "Having reviewed the video footage and spoken to Luis, his behaviour is unacceptable and I have made him aware of this."
Chelsea interim head coach Rafael Benitez, the former Liverpool manager, said he did not see the incident.
Suarez, 26, has regularly hit the headlines since joining Liverpool from Dutch club Ajax two years ago.
He has frequently attracted criticism for diving and was banned for eight matches after being found guilty of racially abusing Manchester United's Patrice Evra during a game in October 2011.
In an apparent precursor to Sunday's incident, he was once banned for seven games for biting PSV Eindhoven midfielder Otman Bakkal while playing for Ajax during a Dutch league game in November 2010.
He left Ajax for Liverpool before he could complete his suspension.
Suarez's strike on Sunday took his tally for the season to a league-leading 23 goals, but Chelsea goalkeeper Petr Cech said his antics were sullying his reputation.
"I didn't see it at the time but people have told me, which is surprising," he said.
"Suarez always does little fouls and pushes. I saw Branislav's reaction and he was not happy at all."
Former Liverpool manager Graeme Souness, now a television pundit, labelled Suarez's behaviour "embarrassing" and said it had put his future at the club in jeopardy.
"He's making it very difficult for himself to stay at Liverpool. That puts him in the last-chance saloon," Souness said.
"He is risking everything this great club stands for."
However, Liverpool captain Steven Gerrard said Suarez's exploits in the second half did not deserve to overshadow his achievements this season.
"I think it would be an injustice to Luis Suarez to talk about 45 minutes -- he has been the best player in the league by far this season," said the England skipper.
"When you play big Premier League games against Chelsea, things are going to get spicy."