The chairman of a mosque targeted by multiple petrol bombs, has described the attack as attempted murder. The incident in Grimsby, Lincolnshire, the most serious attack on Muslims since the killing of drummer Lee Rigby, comes at a time of increased activity by far-right groups such as the English Defence League.

A young family with two children were among a number of worshippers inside the building praying on Sunday night when three petrol bombs were understood to have been thrown through the entrance and fire exit.

Two men, aged 33 and 37, were arrested by police patrolling near the Grimsby Islamic Cultural Centre. Security around the mosque had been stepped up after a brick was thrown at it on Thursday.

The mosque's 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."

The mosque's imam, Ahmad Sabik, said: "The whole community is really shaken up and there is damage to some of the walls on the inside of our mosque and to the outside of the building because one of the bombs was put in a rubbish bin in the car park."

CCTV footage showed three petrol bombs being thrown over the gate of the building.

Sabik said the attackers were ignorant about teachings of Islam adding that community spirit was holding up despite the assaults. "They obviously don't understand the reality of Islam and what we believe in. We are a religion of peace and we condemn the awful attack on that young man in Woolwich.

"Although we are devastated by both attacks here, there is a great sense of community around here and our spirits will not be broken. We have had countless people come to the mosque in the last few days to offer their support."

Austin Mitchell, the Labour MP for Great Grimsby, said attacks on mosques and other Islamic institutions were playing into the hands of terrorists who wanted community conflict. Speaking to BBC Radio Humberside, Mitchell said: "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."

The Islamic centre in Grimsby is part of a complex that includes a mosque that was targeted by youths last week.

Police said they had arrested 11 people who had been drinking at a nearby house party when things got out of hand. Four 16-year-old boys and a 15-year-old boy have been released on bail until the end of June.

A statement from Humberside police said it was too early to speculate why the fire was started and could not say whether the incidents were linked but 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."

Chief Superintendent Tony Forbes said: "The immediate response by officers, to both incidents at the mosque on Weelsby Road in Grimsby led to a number of arrests being made quickly and investigations are under way by detectives from Grimsby police station.

"I would like to remind people that these are serious offences which are being investigated and those who are responsible will be brought to justice. It is important to remember that those people who have committed these offences are a very small minority and they do not reflect the vast majority of people who live in north-east Lincolnshire.

"The people who want to engage themselves in this type of criminal activity will be dealt with using all appropriate police resources and powers. I have spoken to community leaders and what is clear to me is the attacks will not be allowed to undermine the very good community relations in north-east Lincolnshire. My officers will continue to work with all of our communities to protect them and ensure their safety."