England midfielder Dele Alli says his middle-finger gesture during the World Cup qualifying win over Slovakia was aimed at team-mate Kyle Walker.
Television pictures showed Tottenham's Alli gesturing in the 77th minute of Monday's 2-1 victory at Wembley.
The incident occurred after he was body-checked by Martin Skrtel, and referee Clement Turpin waved play on.
"Just to clarify, the gesture was a joke between me and my good friend Kyle Walker," Alli, 21, wrote on Twitter.
"Apologies for any offence caused."
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Football's governing body Fifa says it is awaiting match reports from officials, which it should receive by the end of the week, before deciding whether to open any disciplinary proceedings.
It initially appeared that Alli gestured towards Turpin, with whom he also had words when he was substituted in the 93rd minute.
Alli and full-back Walker were team-mates at Spurs until the latter joined Manchester City this summer.
England manager Gareth Southgate said the duo were "messing about", adding: "They have a strange way of communicating."
Alli's temperament has previously been questioned.
He missed the Premier League title run-in in 2015-16 after punching West Bromwich Albion's Claudio Yacob, and was sent off for a dangerous foul on Gent's Brecht Dejaegere during a Europa League game last February.
England started Monday's match poorly, falling behind to Stanislav Lobotka's third-minute goal.
Eric Dier levelled with a near-post finish following a corner, before Marcus Rashford shot home for a much-improved home side.
England are five points clear of second-placed Slovakia in Group F with two games left to play.
The group winners qualify automatically for next summer's World Cup in Russia, while the runners-up face a play-off.