Police say they are treating the incident as a hate crime.
Officers were called at around 9.30am and cordoned off the area while they investigated.
They are now reviewing CCTV footage and working closely with the mosque’s Imam.
Neighbourhood police team officer, Insp Al Lloyd, said: “This is a matter that we are taking extremely seriously and we will not tolerate hate crime in this area. We are pursuing a number of lines of enquiry and I would urge anyone in the community who has any information about this incident, or who knows who may be responsible, to contact police urgently.”
The incident is the latest in a string of attacks on the mosque.
For a full report pick up a copy of the Newbury Weekly News on Thursday.
Meanwhile anyone with any information should contact the police on the non-emergency number 101.
Alternatively the Crimestoppers charity can be called anonymously on 0800 555 111 or online at crimestoppers-uk.org