A "smash-and-grab" robbery has taken place at Selfridges department store on Oxford Street in central London.
Men armed with axes smashed glass cabinets and made off with a number of items, a Metropolitan Police spokesman said.
Two people were later arrested after they came off a moped and members of the public stopped them fleeing until officers arrived.
Selfridges later tweeted that no-one was hurt in Tuesday evening's robbery.
Onlookers posted photographs of the scene on Twitter, including one showing tiny pieces of broken glass and another showing two axes.
Matthew Carrozo, from east London, said he later heard the moped crashing just under a mile away from Selfridges and saw one man dressed in full motorcycle gear while a second man dressed in a burka fell on to the ground.
'Kicking and screaming'
The 28-year-old, who was on the corner of Goodge Street and Charlotte Street, said he then saw a man run out from a nearby pizza restaurant and pin down one of the two people who were on the vehicle.
"Someone noticed a bag had fallen off the moped and that it had opened and a bunch a watches fell out," he said. "The duffle bag was full of watches and jewellery."
"The first guy pegged it down Charlotte Street and then he was held to the ground as other people were getting involved. He really put up a struggle.
"When cops turned up they put him in the back of a van and he was kicking and screaming," said Mr Carrozo.
One of the arrested men was taken to hospital, but his condition is unknown. The second man is currently in custody.
Sally Boazman, who was in the store when the raid happened, said: "Suddenly I saw hundreds of people running to the door.
"People started to panic. It was a real panic situation."
Selfridges posted on its Twitter feed: "Hi, we just want to let you know that everyone is safe and the police are investigating. We will update you once we have more information."
The raid took place 30 minutes before the world famous department store was due to close at 21:00 BST.
A Metropolitan Police spokesman said: "It is not currently known how many people were involved.
"Armed officers attended but no shots were fired."