“I am concerned to hear of the incident at Manchester Central Mosque last night,” Starmer said on social media, adding “this will be worrying for Muslim communities, especially during Ramadan”.
“We will not and must not relent in the fight against anti-Muslim hatred,” the prime minister told MPs later.
Police in Manchester, northwest England, said they responded to reports Tuesday night of two men entering Manchester Central Mosque carrying “offensive weapons while people were worshipping during the holy month”.
Officers arrested one man in his 40s on suspicion of carrying an offensive weapon and possession of drugs.
“We quickly responded to the scene where we searched the suspect, arrested him and seized weapons, including an axe, a knife and class B drugs,” Manchester police assistant chief constable John Webster said.
Police said they were trying to identify the second man.
No threats were made and there were no reported injuries, according to the police force.
“At this time, it is not clear what the circumstances or intent, if any, was around this incident,” Webster said, adding that patrols around mosques had been increased.
In a statement on social media, Manchester Central Mosque said: “The Muslim community in the UK has experienced a notable rise in threats and hostility over recent years.”
Two Jewish people were killed last year in an extremist attack at a Manchester synagogue on Yom Kippur, the holiest days of the year for the community.
Last October, UK police also probed a suspected arson attack at a mosque in the coastal town of Peacehaven in southern England as a “hate crime”.
“I remember visiting Peacehaven Mosque in the wake of the awful attack there,” Starmer told parliament, adding the government had committed £40 million (US$54 million) to protect mosques and community centres.
“We’re establishing a new fund to monitor anti-Muslim hatred and support victims… We will fight hatred and protect freedom of worship in this country.”
Religious crimes in England and Wales, excluding London, went up by three percent from 2024 to 2025 according to official figures, with over 7,000 incidents recorded by police in the year ending March 2025.