Two people have been arrested on suspicion of arson following a fire at an Islamic cultural centre in Grimsby, Lincolnshire.
CCTV appears to show three petrol bombs being thrown over the gate of the building on Weelsby Road.
Sky's North of England Correspondent Gerard Tubb, who has seen the footage, said they hit a door, wall and rubbish bin.
"A man then rushed out of the mosque and through the flames before grabbing a fire extinguisher to put the blaze out," he said.
Diler Gharib, chairman of the mosque, 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."
The mosque was targeted last week when a brick was thrown through a window, shattering a pane of glass that fell onto a sofa below.
There had been a police presence around the building and an officer arrived moments after the fire was extinguished.
A spokesman for Humberside Police said no one was injured in the fire.
He said officers had discovered a number of messages on social networking sites that appeared to invite people to meet at various locations in the area and cause trouble.
"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," he added.
The murder of soldier Lee Rigby in Woolwich last week has provoked a backlash of anger across the country , with reports of a large increase in anti-Muslim incidents and malicious comments on social networking sites.
In Walsall, two men were charged with racially aggravated public order offences following an English Defence League protest.
The pair - a 22-year-old from Walsall and a 28-year-old from Wolverhampton - will appear before magistrates on June 18.
Faith Matters, an organisation that works to reduce extremism, said more than 160 incidents had been reported to its helpline since Drummer Rigby's death.
That compares to an average of four to eight cases a day reported to the group before the attack.
However, Humberside Police said it was too early to speculate about why the fire at the mosque in Grimsby was started.
:: The force is urging anyone with any information which could assist their investigation to call the force's non-emergency number 101, quoting log number 778 of 26/05/2013.