An explosion which left nails and debris strewn outside a mosque was "an act of terrorism", police have said.
The blast happened on a disused railway line near Binfield Street in Tipton in the West Midlands at about 13:00 BST.
A nearby shopkeeper said: "I did tell the police there to evacuate the area, please for god's sake - there were nails all over the place."
Counter terrorism officers were called in and the surrounding area was closed off for several hours.
'Terrified and shaken'
Shopkeeper Sadarat Khan said he was coming out of a local chemist when he heard a "bomb blast".
"They [the police] didn't seem to be bothered too much... It took them about 40 minutes to evacuate the place," he said.
"People were terrified and very scared and shaken."
Resident Raja Khan was about 50m away when he heard the blast and said a device was found on a wall on the disused railway line at the back of the mosque.
He said: "A few kids came out shouting, 'bomb, bomb'. There were branches that came off trees all over the place."
He said he went to the mosque fearing there would be casualties.
"If it had been when prayers were going on there would've been 300 to 400 people there. There were about 22 to 25 people I think at the time.
"People are terrified for their kids, myself included."
Asst Ch Con Gareth Cann said whoever was responsible "wanted to cause serious harm".
"I can't say for sure it was directed at the mosque, but from what we've seen this seems to be the most likely option," he said.
Minor damage was caused to a window of a nearby house, he said.
A counter terrorism investigation has been started, the force confirmed.
It is understood the explosion centred on an embankment near a disused rail line running behind the mosque.
In a joint statement, the board of trustees and management committee of the Kanzul Iman Central Jamia Mosque said: "We express our deep shock and utter dismay regarding the incident that has occurred this afternoon.
"On behalf of the local community, we condemn this senseless and mindless act. It's a blessing from God that thankfully no-one was injured in the blast.
'Day of funeral'
"We call for calm and strongly urge the community not to let this incident divide us and cause disharmony.
"We stand united, stand together in the aftermath of this mindless act."
Police lifted most of their cordons at about 21:00 BST but said Binfield Street was likely to remain closed overnight on Friday.
Officers gave bottles of water to residents with young children who gathered along Dudley Port in Tipton during the afternoon.
Local councillor Ian Jones said he was "very shocked" by what had happened.
He told BBC WM it could not "go unnoticed" that the incident happened on the same day of the funeral of Fusilier Lee Rigby, who was killed in Woolwich in May.
Councillor Syeda Amina Khatun said she was not aware of any previous attacks on the mosque.
"The whole estate has been blocked off. People are surprised that something like this has happened," she said.
The mosque is the central place of worship for Tipton's long-established Muslim population.
The explosion pushes the community back into the headlines after three men from the town were captured in Afghanistan in 2002 and taken to Guantanamo Bay.
Ruhal Ahmed, Asif Iqbal, both 22 at the time, and 26-year-old Shafiq Rasul were dubbed the "Tipton Three" and held at the US camp in Cuba for two years.
They were eventually returned to the UK in March 2004 where they were released without charge.
West Midlands Police are still investigating an explosion which occurred near a mosque in Caldmore in Walsall last month.
About 150 people were evacuated from homes near the Aisha Mosque and Islamic Centre after a device was found in a nearby alley.
Mr Cann told the media there was nothing to suggest a link between this incident and what occurred in Tipton.