British law enforcers and intelligence services are now trying to get to the bottom of a reported plot by Islamic State terrorists to attack the Victory over Japan Day commemoration ceremonies in London this weekend, allegedly using a pressure cooker bomb similar to the one used in the Boston Marathon bombing in 2013.

Sky News learned of the plot from a certain Sally Jones, a British convert to Islam fighting for ISIS, Fox News wrote. Jones relayed the information to undercover reporters, who gave her the impression that they were also keen on joining the ranks of ISIS fighters. Jones told them she had previously instructed three British nationals to carry out the attacks.

She also told the undercover reporters that the ISIS policy now is for underground jihadists to remain in their home countries and wait for the order to attack.

Sky News said it already alerted London's Metropolitan Police about the plot against the V-J Day celebrations, which will be attended by dignitaries such as Queen Elizabeth II, British Prime Minister David Cameron, and World War II veterans, aside from the thousands of spectators.

According to The Daily Mail, the reported terrorist plot, described as a possible assassination attempt on the Queen and possibly Prince Charles as well, has led to an urgent review of security preparations.

Despite the threat, the Metropolitan Police issued a statement encouraging people to attend the celebrations.

"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," the Metropolitan Police said.

"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."

No arrest has been made yet but counter-terrorism authorities are already monitoring developments.

The July 7, 2005 London bombings, the deadliest terror attack in UK in recent years, left 52 people dead and more than 700 wounded after four suicide bombers attacked Tube trains and a bus.