The death of Osama bin Laden has sparked fears of revenge attacks in the UK, putting Britain on a high alert.

Foreign Secretary William Hague said that al Qaeda are likely to retaliate for the killing of Osama bin Laden: “We must remember that this is not the end of being vigilant against al Qaeda and associated groups, and, in fact, there may be parts of al Qaeda that will try to show that they are still in business in the coming weeks, as indeed some of them are.

“This is a very serious blow to al Qaida but, like any organisation that has suffered a serious blow, they will want to show in some way that they are still able to operate”.

Osama bin Laden: Did WikiLeaks play part in his death?

Osama bin Laden: Details of US strike emerge

“We will still have to be vigilant – even more vigilant – in the coming days about the international terrorist threat,” he added.

Home Secretary Theresa May also praised the recent events saying that bin Laden’s death was “an important and significant development in the struggle against global terrorism”.

She did, however, stress  that there was still a “real and serious threat”, and called for the public to help the police in their fight against terrorism.

“There is a continuing need for everyone to remain vigilant and to report any suspicious activity to the police,”

Not long after the news of Osama bin Laden’s death was announced, wild celebrations in New York City and Washington broke out.

“I am paying my respects,” Jonathan Simmons, 53, told The Independent. “There is a sense of celebration I see, but I feel like we are freeing the spirits of those who died here to a better place.”

Meanwhile, many relatives of the 9/11 victims said they felt averse to the joyful celebrations of the killing of bin Laden.

Al Santora, who lost his 23-year-old son Christopher in the 9/11 attacks, told Reuters: “It was a great feeling to hear this, but as I said, it’s a mixed emotion. It’s a rollercoaster ride, you’re happy one moment and sad the next moment. No matter what happens, nothing is ever going to bring these people back.”

Rosaleen Tallon, the sister of 9/11 victim Sean Tallon, said that she felt hesitant to celebrate the news of bin Laden’s death.

She said: “Especially living in New York, it’s personal to us. And I don’t want it to become this political — like ‘Oh, this is the most wonderful thing that’s happened,’ it is a small victory, but I think it is a victory that needs to be tempered with caution.”