British officials said Monday they have stopped a dozen “Islamist terror plots” since March of 2017, when a man drove a car into a crowd of pedestrians on the Westminster Bridge.

Andrew Parker, the chief of MI5, said in a speech hosted by Germany’s domestic intelligence service that the United Kingdom (U.K.) has thwarted 25 attacks since 2013.

He warned that the threats will continue, even as the U.S., U.K., France and other allies make progress in the fight to eliminate the Islamic State in Iraq and Syria (ISIS).

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“Whilst Daesh has now lost its false caliphate in its strongholds in Syria and Iraq, tackling the group as a movement will require sustained international focus for years to come,” Parker said, using an Arabic term for the group. “As I speak today, they are seeking to regroup and the threat will persist."

He argued that European nations must work together to combat future terrorist threats and urged collaboration between law enforcement agencies and social media and communications companies.

Since 2016, Parker said, there have been 45 attacks across seven countries: the U.K., Germany, France, Finland, Belgium, Spain and Sweden.

Parker noted that next week will mark one year since the bombing at an Ariana Grande concert in Manchester.

Parker's comments come just days after a Chechnya-born Frenchman killed a man in Paris in a knife attack.

ISIS claimed responsibility for the attack, though authorities said they were still working to determine the veracity of the claim.

The White House condemned the attack, and President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE suggested countries may have to make "changes to our thought process on terror."