Islamophobic slogans have been painted onto a building near a mosque and cultural centre, according to police.
The "offensive remarks" are being removed from the building and London mayor Sadiq Khan promised that the "criminals will face the full force of the law".
It comes just days after "sickening" antisemitic graffiti was found scrawled on a synagogue and shops elsewhere in London.
Officers were called to the building – near the North Brixton Islamic Cultural Centre in south London – after reports of "anti-Islamic slogans" being spray painted on walls.
The police is working with Lambeth Council to remove the remarks as soon as possible, the force said, and enquiries are ongoing as part of a full investigation.
Mayor of London Sadiq Khan wrote on Twitter that he was "disgusted" by reports of the graffiti and said that such prejudice is "cowardly".
"Disgusted to hear that Islamophobic slogans have been spray painted near the North Brixton Islamic Centre," he said.
"[The Metropolitan Police] are working with Lambeth Council to have them removed, but let me be clear: all prejudice is cowardly and criminals will face the full force of the law."
Local MP Florence Eshalomi called the incident "disturbing" and urged anyone with information to contact the police.
Miqdaad Versi, a spokesperson for the Muslim Council of Britain, said it was "worrying to hear about this racist incident".