A 46-year-old man was arrested on Monday afternoon on suspicion of arson with intent to endanger life, Sussex Police said. He is currently in custody.
Emergency crews were called to the fire in Peacehaven’s Phyllis Avenue at about 9.50pm on Saturday 4 October.
Footage showed two people, wearing dark clothing and face coverings, approach the front door before spraying something on the entrance and igniting a fire.
Sussex Police said no one was injured in the blaze, however the front entrance of the mosque suffered significant damage, as did a nearby car.
The force said it was treating the incident as a hate crime.
Detective Chief Inspector Mark Cullimore, from the Surrey and Sussex Major Crime Team, said: “The investigation is progressing at pace, and we are pursuing all lines of enquiry to identify those responsible for this appalling and reckless attack.”
Officers are continuing to appeal for information on the incident and anyone with any knowledge, “no matter how small you think it might be”, is being urged to contact the police.
Superintendent Rachel Swinney said: “We acknowledge the serious distress and concern this has caused in our communities.”
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There will continue to be an increased police presence at the scene and extra patrols are operating at places of worship across Sussex, she added.
Ms Swinney continued: “We will continue to engage with our religious communities to support them and ensure their concerns are heard and acted upon.”
