Police are searching four properties in the capital
Three men have been arrested in north London on suspicion of terrorism.
The men, aged 40, 22 and 30, have been taken to Paddington Green police station, where they remain in custody.
They were arrested under the Terrorism Act 2000 on suspicion of the commission, preparation or instigation of acts of terrorism.
It is thought the three men were suspected of attempting to set fire to a publisher's office in Lonsdale Square, the BBC understands.
Two men were arrested outside a property in Lonsdale Square, and the third following an armed vehicle stop near Angel Tube station on Upper Street at 0225 GMT on Saturday.
A small fire was put out at a property in Lonsdale Square, which is used as a home and office by publisher Martin Rynja.
His company, Gibson Square, recently agreed to publish a controversial novel about the Prophet Muhammad and his child bride, entitled The Jewel of Medina.
The men were arrested by armed officers from the Metropolitan Police's Counter Terrorism Command in a pre-planned, intelligence-led operation.
Police are searching four properties in Walthamstow, Ilford and Forest Gate.
Francesca Liebowitz, 16, who lives in Lonsdale Square with her parents, said: "The police couldn't get the door open so the fire brigade battered it down.
"There was smoke coming from around the door, but I don't know whether that was because of the door being broken down.
"They evacuated people from the house. It's a bit scary to have this happen on your doorstep, nothing like this has ever happened round here before."