Muslim leaders have condemned the bombing attacks

Forensics experts are also analysing a racist letter sent to the same mosque, hoping to find out who sent it.

The mosque received the letter on Saturday, with the break-in and animal parts also left over the weekend.

It is not known if the incidents are linked. Community leaders said they were "shocked".

The letter followed the London bombings, which killed 55 people.

It was sent by first class post and was reportedly signed by a number of people.

We must not let bigots and racist use the horrific murders in London as an excuse to persecute Muslims Cllr Mohammed Islam

The content has been described as "religious hatred against Islam".

Councillor Mohammed Islam said that the letter had caused "deep worry" among the Muslim community in Cardiff.

"It has been really shocking for the community," he said.

"There are some major concerns among people about what has happened.

"The police have taken away the letter for forensic tests and are investigating what has happened.

"I strongly condemn these acts and I call on everyone in the community to condemn this kind of activity.

"We must not let bigots and racist use the horrific murders in London as an excuse to persecute Muslims.

"I am calling on everyone in the community to be calm and not to get involved in extreme acts of any kind.

"The bombs in London were not to do with the Muslim communities, they were carried out by extremists who did not care who they killed," he added.

Letter seized

He confirmed that police were also investigating a break-in at the weekend and animal parts being left.

A spokesman for South Wales Police confirmed that the "abusive letter" had been taken away for forensic examination.

Officers have visited the mosque but the force said that despite other areas of the UK suffering more racial hatred attacks, incidents in south Wales have been "few and far between".

The spokesman said: "We can confirm that a racially abusive letter was sent to the mosque.

"It has been seized by South Wales Police and has been sent away for forensic tests.

Councillor Islam is asking for calm within communities

"Community officers have met up with officials from the mosque to offer reassurance and officials from the mosque are happy with the policing arrangements that are in place."

However, some south Wales based Muslims say that the London bombing has increased racially motivated insults.

"I know of people who have been spat at on streets, ignored by previously friendly neighbours, my dad was hassled, mum was taunted by a guy pretending to scare her," said one Cardiff resident who did not want to be identified.

"Muslims are scared to even go to the park. Roath Park is normally is filled with people of all colours, but last weekend all you could see was caucasian families.

"The Muslim community are scared," she added.

Meanwhile, Plaid Cymru assembly member Owen John Thomas, who met mosque leaders, said: "The posting of threatening letters and animal parts to a mosque is clearly intended to insult and frighten our fellow citizens.

"I hope that people of all cultures will unite to show their support for those who worship at the mosque."