The International Olympic Committee (IOC) said it would look into the refusal by Egyptian judoka Islam El Shehaby to shake the hand of his victorious Israeli opponent Or Sasson after their first round match in the men’s over-100kg competition at the Rio Olympic Games.

Sasson won the bronze medal in his event.

In judo it is customary to both bow to opponents and shake hands after a bout is over.

El Shehaby had been well beaten but stood impassively and then backed away as Sasson tried to shake his hand.

As he left, El Shehaby was called back to the center by the referee to bow. But he was then loudly jeered out of the arena by angry supporters.

He later announced he was quitting judo.

The 32-year-old Egyptian, a world championship medalist in 2010, had faced pressure on social media and from hardline Islamist groups in his homeland to withdraw from the fight.

Mark Adams, the IOC Director of Communications, said “Things happen in the heat of the moment that are not acceptable.”

“We believe the Olympic movement should be about building bridges, not erecting walls. There’s absolutely no excuse for it.”

“It’s a shame if that happens,” he said.

Ofir Gendelman, spokesman for Israeli Prime Minister Benjamin Netanyahu, called the incident “shocking.” In a Twitter post, he said it “goes against the spirit of Rio 2016,” writing in Arabic that “sports are not the field for politics and extremism.”

Israel and Egypt have a peace treaty since 1979.

On Sunday, the head of Lebanon’s Olympic Committee was summoned by the Rio Games’ organizers for a dressing down, following a kerfuffle with the Israeli delegation after the two teams were told to share a bus to the opening ceremony.

The Lebanese delegation refused to allow the Israeli players to board the bus, leading to a spat that injected politics into the Games’ opening.