Thames Valley Police said the items were found at the mosque on Manzil Way in the early hours. The flag had been attached to one of the building’s doors.
In a statement posted on social media, the mosque said its volunteers and the Imam had cleansed and purified the entrance.
The Oxfordshire Civic, Community and Faith Leaders group said it was “deeply shocked and saddened” by the incident, calling it an “assault on the core values of respect, dignity and unity that we cherish in Oxfordshire”.
“Our hearts are with the Muslim community of Oxford”, it said.
“We extend our full solidarity and support to the worshippers, the imams and the management of the Central Mosque, who have shown immense strength and grace in response.”
Police have appealed for witnesses and anyone with information to come forward. The mosque remains open, with officers providing reassurance to worshippers and increasing patrols in the area.
Chief Supt Ben Clark described the incident as “a provocative act to upset and offend mosque users”, stressing: “Such behaviour has no place in our community and we will do everything in our powers to bring anybody involved to justice”.
