Saleh Al Arif spoke out after Mohammed Syeedy, 21, was jailed for 24 years over the murder of Jalal Uddin, 71, who was bludgeoned to death in a children's playground in February, The Guardian reported on Sunday.
He said: "I spoke to some members of the community. They are really worried about the IS supporters. They believe there are a lot of supporters in the Bengali community. From the outside, it's like they are doing something good, charitable work and other things."
"They believe they are just trying to make a good impression and they are radicalising the young people in the community and they simply don't want to see that. They are very scared and they believe they have some kind of link with the IS. They just want to get rid of it and they want help from the police," Arif added.
Jalal Uddin was murdered by Syeedy and Mohammed Abdul Kadir, 24, because the elderly scholar practised a form of Islamic healing in which he gave away amulets, called taweez, to the sick -- a practice denounced as black magic by the IS.
The trial at Manchester crown court heard that Syeedy, Kadir and their friends surveiled Jalal Uddin for 18 months before he was murdered on February 18. Kadir was being sought by police after he flew to Istanbul, Turkey, three days after the killing.
In an interview with Sky News, Arif said he believes others were also involved in his father's murder who "knew what's going to happen", although they did not participate in the attack.
"Someone should be keeping an eye on these people. It should be investigated properly," he said, while also praising the police investigation.
"He was very religious, very peaceful and very knowledgeable. He had no political views but he had strong religious views and what he believed he tried to practise it to the death," he added.
In a victim impact statement read to court on Friday, Arif said his father told him two days before he was killed that he planned to return to Bangladesh later this year for the first time in 15 years.
Jalal Uddin had not seen his wife, children or grandchildren since he left Bangladesh for Britain in 2002.
