Police are investigating after red paint was daubed on the entrance of an office headquarters in the Square Mile.
The Walbrook Building near Cannon Street was targeted by suspects who also smashed windows at around 2am.
They then dispersed towards Bank and a search by officers could not locate them, City of London Police said.
According to global security experts, preliminary indications suggest incidents at The Walbrook and other buildings are linked to pro-Palestinian groups.
“The methods used are consistent with recent actions carried out by proscribed organisations,” they claim.
Footage shared on social media shows the exterior of the 12-floor building - opposite the Bloomberg Arcade - covered in paint. The office block is close to St Paul’s Cathedral and Mansion House.

Superintendent Jesse Wynne, of City of London Police, said: “Just after 2am this morning, City of London Police were alerted to four individuals damaging a commercial premises near Bank.
“The suspects smashed windows and sprayed the front of the building with red paint before dispersing via Bank.
“The area was searched but no suspects were found to still be in the area.
“Investigations are ongoing and no arrests have been made at this stage.”