Two people have been arrested on suspicion of arson after a mosque in Grimsby was set alight.
Petrol bombs were thrown into the Islamic cultural centre on Weelsby Road while a young family were still inside, according to reports.
The fire was extinguished and no one was injured as a result, Humberside police said.
It was the second suspected retaliation attack after the killing of drummer Lee Rigby in Woolwich last Wednesday. Bricks were thrown through the window of the mosque on Thursday. However police said it was too early to speculate on motive.
Chairman Diler Gharib told the Grimsby Telegraph: "We had just finished our prayers and were discussing how to thank our neighbours for the support they have shown us over the past few days when we heard a bang and saw fire coming under the door.
"I grabbed a fire extinguisher and put it out and then two more petrol bombs hit the fire escape and the bin so I had to put those out too.
"Luckily the police have been monitoring the mosque since the last attack and they were able to arrest two people almost straight away.
"We have all been feeling on edge and now this has happened. It's not just the people at the mosque we are worried about, it's our wives, daughters and children who are out in the community."
"People need to realise that the people who committed the murder in Woolwich are criminals and it had nothing to do with the Muslim faith."
A spokesman added: "The force is currently aware of a number of messages which have been posted on social networking sites by a small minority of individuals.
"These messages appear to be an attempt to incite trouble by posting messages inviting people to assemble and cause trouble at particular locations.
"Those people should be aware that we are monitoring these sites in Humberside and we will take action against those intent on attempting to incite violence or post messages of a racial nature."
Following last night's incident, Great Grimsby MP Austin Mitchell said attacks on mosques and other Islamic institutions were playing into the hands of terrorists who wanted community conflict.
Mr Mitchell told BBC Radio Humberside: "It's sheer, simple stupidity.
"I'm appalled and shocked. I didn't expect this in Grimsby
"These idiots, whoever they are, are playing directly into the hand of the terrorists."