Video tapes and DVDs left at mosques in Dewsbury contain "distasteful and offensive" propaganda material, a senior police officer has said.
One of the mosques in Dewsbury where the tapes were left
The recordings were left at entrances to two mosques in South Street, Savile Town, not far from where 7 July London bomber Mohammed Sidique Khan lived.
Ch Supt Barry South said the fact they had been handed in showed co-operation from the local community.
"People locally have been increasingly vigilant, as we asked them to be."
Mr South, divisional commander for Kirklees, said residents had so far handed over six or seven copies of the DVD to police.
"When they have discovered something that they feel may have an impact on their community they have had the confidence to come forward to us and make us aware so that we can look into the matter," he said.
Safiq Patel said the community was worried by the tapes
"The video is being looked at in depth by officers who inform me that the main content is propaganda material.
"In the main it can be described as distasteful and offensive but we believe that it is material that can be downloaded on the internet and has been used on national media networks already."
He thanked the community for handing in the recordings and urged anyone with any other copies in circulation to hand them in.
"We do need to know who has done this, why, and what their overall purpose has been," Mr South said.
"I'm aware that some people locally have seen the video, found it distasteful and destroyed their copies, but if there are others in circulation then please let us have them."
Mr South said the two mosques in South Street were totally unaware the DVDs had been left.
He said they were placed at entrances and exits, not in the mosques themselves. Local resident Safiq Patel alerted police to the tapes but said he did not know who had left them.
He had not seen one himself, but added: "As far as we know the videos were a portrayal of violence - a portrayal of Muslims being victims of violence.
"It was an attempt to portray Muslims as victims and to perhaps try and evoke local sympathy, local pressure into some sort of backlash towards the perpetrators which I think the videos portray as British and American politicians - European democracies as the enemies.
"I believe they were aimed at stirring up racial tension - stirring up concern in the community.
"I think the broadest aim may have been recruiting terrorists in the future.
"It's worrying the local community. There's a lot of people round here who want peace, who have children, grandchildren, who have worked very hard to establish the mosques, the houses, the communities that we have.
"They do not want that blown to pieces by anybody - by intruders, by outsiders and by al Qaeda for that matter."