Video posted on Twitter showed anti-war activist Sam Walton approaching Assiri.

Britain has apologized after an egg was thrown at a Saudi military official during a visit to London, Saudi state media said Sunday.

An anti-war activist last week attempted a citizen’s arrest of General Ahmed Assiri, spokesman for the Arab coalition fighting militias in Yemen, before another threw an egg that hit Assiri in the back.

British Foreign Secretary Boris Johnson called Saudi Arabia’s Deputy Crown Prince Mohammed bin Salman, the kingdom’s defense minister, to apologize for “the attack on General Ahmed Assiri, counsellor to the prince, by protestors,” the state-run SPA news agency said.

Assiri told AFP he had been “subject to aggression” by protestors critical of Riyadh’s operations in Yemen.

Video posted on Twitter showed anti-war activist Sam Walton approaching Assiri, putting his hand on the general’s shoulder and announcing he was placing him under citizen’s arrest before being pushed aside by security personnel.

British Foreign Secretary Boris Johnson called Saudi Arabia’s Deputy Crown Prince Mohammed bin Salman to apologize.