"I have not seen this tactic in the United Kingdom before where terrorists create maximum fear by strapping fake explosives to themselves", said police commander Dean Haydon, who is leading the investigation.
The fake suicide belts were made up of leather belts, with water bottles covered in tape attached.
One of the first officers on the scene of last weekend's terror attacks in London described scenes of chaos and confusion, with wounded on the pavement and police unsure whether gunfire they heard was from the attackers.
The fake explosive belts were visible during the attacks, Haydon said, and may have looked real to those who saw them.
Police Commander Dean Haydon speculated that the bloodthirsty zealots might have worn bomb props "as protection from being shot themselves".
Police are questioning seven suspects over suspected links to the attackers, Pakistani-born British citizen Khuram Butt, Moroccan Rachid Redouane, and Youssef Zaghba, an Italian national of Moroccan descent.
Forty-eight people have been taken to hospital after a terror attack in central London in which six people died, the London Ambulance Service said Sunday.
Butt, who police consider the attack ringleader, had been on bail after being arrested for fraud in a case in October of previous year, police said.
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The 41-year-old and his officers rushed to Borough High Street and made their way on foot to the market where the attackers were looking for people to kill.
The van was packed with sacks of gravel and chairs, possibly to increase its weight as a "battering ram".
"I asked my officers to form a cordon to stop the public from going into the market, and that's when the shooting started just behind us".
Police released details of their investigation as they appealed to the public for information, saying that showed Khuram Butt, believed to be the plot's ringleader, originally tried to rent a 7.5 ton truck.
After leaving the vehicle, the terrorists used 12in ceramic knives with pink blades in a stabbing spree.
After word came that the threat was over, he told people in the pub that they were safe, according to the account. Where might the attackers have bought them from?
"In terms of our witnesses that we've spoken to so far, out of the 300 odd people, there are about 20 different countries of origin".