Counter-terrorism police arrested a 22-year-old woman on suspicion of supporting Hamas at a protest in Brighton.
The Anti-Terrorism Police South East (CTPSE) said the woman was arrested on Thursday under Section 12 of the Anti-Terrorism Act 2000.
It comes after an investigation was launched focusing on a speech given by a woman at the protest in Brighton on Sunday.
Superintendent Petra Lazar of Sussex Police said: “After reviewing footage of the protest event held in Brighton on Sunday 8 October, the matter was investigated by South East Counter Terrorism Police. We will continue to support them as they carry out their investigation.
“We are aware that the ongoing conflict in Israel and the Gaza border is raising public concern and impacting communities globally and locally, and we extend our support to those affected in Sussex.
“Sussex Police have increased their visibility in parts of Sussex to provide a greater presence and reassurance to our local communities.
“We recognize there is potential for tensions to rise and we are collaborating and working with communities and partners to ensure people feel safe and secure.”