Police successfully foiled a plot to explode a pressure cooker bomb at a parade in south London today, it has been confirmed.
According to The Sun newspaper, a suicide plot was intended to strike an Armed Forces Day parade targeting soldiers from the unit of murdered Lee Rigby, but failed after one of its leaders in Syria unwittingly recruited an undercover investigator from the newspaper to carry it out.
It is alleged that a leading IS figure, identified as Junaid Hussain, who was originally from Birmingham, told the investigator: "It will be big. We will hit the kuffar (unbelievers) hard InshAllah. Hit their soldiers in their own land. InshAllah. Soldiers that served in Iraq and Afganistan will be present. Jump in the crowd and detonate the bomb.
"They think they can kill Muslims in Iraq and Afghanistan then come back to the UK and be safe. We'll hit them hard InshAllah," he is reported as saying.
A Scotland Yard spokesman said: "The police, together with our security partners, remain alert to terrorist threats that may manifest here or where individuals overseas may seek to direct or inspire others to commit attacks in and against the UK.
"It is always helpful when journalists share with us information, as The Sun did in this case, that could indicate terrorist or criminal activity. Attacks yesterday show the global nature of terrorism and the threat level in the UK from international terrorism remains unchanged at severe.
"While the UK threat level from international terrorism remains severe, we would like to reassure the public that we constantly review security plans for public events, taking into account specific intelligence and the wider threat.
"Our priority is the safety and security for all those attending or involved, the public are encouraged to continue with their plans to attend or take part in events as normal. We would also like to reiterate our long-standing advice to remain vigilant and alert.
"As ever we would urge the public to get in touch to report anything suspicious by calling the confidential anti-terrorist hotline on 0800 789 321 or in an emergency by calling 999."
The terror threat level in the UK remains unchanged at severe following Friday's three terror attacks in Tunisia, France and Kuwait.
Speaking after a Cobra meeting Prime Minister David Cameron has vowed that the "terrorists will not succeed. "
At least 65 people are now known to have died in three terror attacks on three continents, all linked directly or indirectly with Isis - also known as Islamic State. The group has warned it will carry out attacks throughout Ramadan, which lasts until 18 July.