Trafalgar Square in London has been evacuated by police following reports of a suspicious vehicle.
Numerous eyewitnesses claim to have heard a loud bang, although police have refused to confirm reports of an explosion, or whether it was a controlled explosion, and instead have said "the incident has been resolved".
Tourist Sarah Churchill who was in Trafalgar Square at the time, with her 11-year-old son Noah, told the Mirror: "I was in the square when the bomb went off."
She said: "There were lots of police, were were just about to walk through the square when we got to corner we saw it was cordoned off.
"We were speaking to a policeman when the bomb went off without any warning.
"He had told us it was a suspicious package, I don't know if was a controlled explosion, but no one told us it was about to go off.
"The policeman looked shocked."
She added: "We could see lots of police and what looked like a bomb squad van, we were just going to walk down to the Mall to see how it was all set up for tonight, when we found the area cordoned off."
Sarah, 38, said the noise of the bomb shook her and described it as like the sound of an IED you would see on the news in Afghanistan.
She said: "It was intensely loud and intensely quick."
She added that her 11-year-old son Noah was terrified as the crowd of 150 panicked and began running away.
"I had nothing to tell him. I didn't know if it was a terrorist, or if they'd be more bombs.
"My son is crying, he's absolutely beside himself.
"We had no idea what had happened, I'm just so glad that nobody appears to be hurt."
Another eyewitness Jon Hansen added: "We were rushed out of the hotel.
"Vehicle left out overnight.
"Saw all four windows of the car smashed out.
"Told us they were waiting for controlled explosion.
"They rushed us down the street. When we reached the other side of Trafalgar (around the back) heard loud explosion."
Shortly after, police said: "The incident has now been concluded and the square will
reopen in due course."
A police spokesman said lots of checks were being carried out in the area, which is a short distance from where a concert is to be staged outside Buckingham Palace later in the day.
He said the incident was believed to have involved a suspicious package.
They later tweeted: "Police attended a report from a member of the public at 09:22hrs of a suspicious vehicle in Trafalgar Square.
"This was investigated and after police took action we have no further concern.
"This was not terrorism related."
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Hundreds of thousands of people are expected in London and along the Mall today ahead of the BBC's Platinum Party at the Palace concert.
Royals are due to arrive at 7.40pm and the open-air concert show in front of the palace, is set to feature stars including Queen, Adam Lambert, Alicia Keys, Duran Duran and Diana Ross.
