A race body claims Muslims in south east Wales have experienced increased abuse since the London bombings.
The South East Wales Race Equality Council (Sewrec) said it had seen a "very big" rise in incidents.
It said the rate of abuse had risen from 10 incidents a month to more than 30 in just two weeks. It also said most were happening in Newport.
A hate letter was sent to a Cardiff mosque this week, but incidents in the Welsh capital appear to be fewer.
Sewrec Chief Executive Dave Phillips said the organisation had reports of a rise in incidents such as verbal racial abuse, threatening telephone calls and even eggs being thrown at people leaving a mosque.
"There has been a very big increase and it is very worrying," he said.
Mr Phillips said that Sewrec operated its own scheme in which people could report racial incidents, a scheme separate from the one run by police.
"There has been nothing as sinister as an actual assault, but the things that have been reported are very worrying," he added.
"We have had reports of people being spat at, being called offensive names, there have even been threats against children. It is very concerning."
He said that although police figures did not indicate a rise in the number of incidents, he believed that it was not a true reflection of what was happening.
"People are very sceptical about what can actually be done about incidents like this and many people don't see the benefit of reporting it to the police," he said.
"Often people feel more comfortable reporting such things to us instead."
Last year Sewrec received 136 complaints of racial incidents but is expecting the figures to rise considerably for the next year.
But its counterpart in Cardiff, Race Equality First, said there was a different picture in the capital.
A spokeswoman said they had not had an increase in the number of racial incidents reported to them.
However, animal parts and a hate letter were sent to a city mosque following the London bombs.
The situation in the south Wales valleys appears to be similar to Cardiff.
Manny Hothi from Valleys Race Equality Council said although reports of racial incidents made to them had not increased, there was anecdotal evidence to suggest that tolerance of people of other faiths was suffering.
He said: "There seems to be a lot of ignorance. One of the staff members heard some people say they wouldn't get on a bus if there was an Asian person on there with a bag for instance.
"People are expressing very negative and ignorant views which has an effect on the minority ethnic communities."
But South Wales Police said that the number of reported racial incidents had not increased in the wake of the London bombings which killed 56 people.
Gwent Police said 36 racist incidents were reported to them between 7 July and 21 July.