British right-wing activist Tommy Robinson said he was detained at Heathrow Airport on Saturday and had his phone seized, after a week during which he posted heavily online about racist and anti-immigrant riots in Northern Ireland.
Robinson, whose real name is Stephen Yaxley-Lennon, said on X that he was held on Saturday evening for around three hours under the Counter-Terrorism and Border Security Act.
"My phone has been seized by the police," he said on X. "Please help kick off my legal fund for defence".
Belfast violence, protests
Robinson tweeted repeatedly last week about violence that swept Belfast after a video went viral showing the brutal stabbing of a man, who lost an eye in the attack. A Sudanese man has been charged with attempted murder. Police have said they are not treating the attack as terrorism.
In the days that followed, rioters targeted homes and businesses owned by ethnic minorities or foreign residents in what the British minister for the province called racist thuggery.
Local politicians have said far-right agitators online had helped to coordinate or promote the violence.
Without naming him, a police spokesman said officers had stopped a man in his 40s at Heathrow Airport on Saturday, following his return to Britain from Russia via Turkey.
"The man was interviewed by officers, and his communication devices were seized. He was subsequently released," the spokesman said.