Police are appealing for information after a vandal attack on a Fylde coast community centre which was being used at the time.
The attack, with stones and lumps of reinforced concrete, left windows smashed and dents in panelling.
People taking part in a relaxation course inside were forced to flee and one woman narrowly avoided injury after glass from a toilet window ended up embedded in a door.
Trustees of the centre said there had been several incidents over a period of evenings with the worst being on October 16.
A Blackpool Council spokesman said: “Such acts of mindless vandalism are deplorable.
“The people who do such things obviously don’t care about a community facility and the people who go there to enjoy activities and socialising.
“We would urge anyone with any information about the culprits to contact the police.”
A police spokesman said: “One of the incidents was reported to us, and the other was picked up on speaking with the staff at the centre.
“There hasn’t been a re-occurrence since and we have stepped up our presence in that area.
“Anyone with information should contact BlackpoolNorthNPT@lancashire.pnn.police.uk and we’d also remind parents of their responsibility to know where their children are and what they are up to.”
Bispham councillor Don Clapham warned that the attack could drive people away from using the centre which was a vital hub for the community to meet in and would cost thousands to repair.
He said: “This was an horrendous attack on the building by youths throwing reinforced concrete blocks through windows while people were using the centre. The cost of the damage could financially ruin this much needed community centre.”