Prime Minister David Cameron confirms that many Britons were victims of Tunisian terrorist attack. Screen grab from PA video for public interest reporting.

At least 15 Britons are among the 39 holidaymakers killed in the Tunisian beach massacre and the Prime Minister warns the UK faces ‘a severe terrorist threat.’

Kalashnikov-wielding student Seifeddine Rezgui targeted Western tourists as he terrorised the popular resort of Sousse.

Tunisian authorities have confirmed the nationalities of 10 of the dead so far, with a Belgian and a German identified alongside the British victims.

Foreign Minister Tobias Ellwood said the Sousse atrocity was ‘the most significant terrorist attack on the British people’ since 7th July 2005, when 52 people were killed.

Mr Ellwood said:

Sadly, I can confirm that at least 15 British nationals were killed in yesterday’s atrocity but I should stress that the number may well rise as several more have been seriously injured in this horrific attack.

Prime Minister David Cameron has warned that the public should be ‘prepared for the fact that many of those killed were British.’

One of those killed is reported to be 24-year-old fashion blogger Carly Lovett from Gainsborough, Lincolnshire.

Miss Lovett, who had only been engaged a few months, was with her fiancee, and they were due to return home today.

Friends and fellow bloggers paid emotional tributes to the former University of Lincoln student on social media.

Some 39 people were also wounded in the attack, including 21 who have already left hospital.

Of the wounded, 25 were British.

Rezgui was said to have laughed and joked as he targeted British and French tourists and sprayed them with gunfire.

He was shot dead by police.

The UK’s terror threat level remains at ‘severe’, the second highest level.

This means an attack is ‘highly likely.’

The UK’s counter-terrorist police in the Met’s Counter-Terrorism Command are now investigating the murder of British citizens and have sent a team of officers to Tunisia.

Assistant Commissioner Mark Rowley, National Police Chiefs’ Council lead for counter terrorism said:

The UK police service continues to support those affected by the terrorist attack in Tunisia by providing a range of specialist officers and expertise.

Extra officers are at British airports to support returning travellers and identify potential witnesses. We are supporting families both in the UK and overseas with specially trained liaison officers, and we are deploying a team of counter terrorism officers to Tunisia to support the UK coroner’s inquests. This includes forensic officers, detectives and other specialists.

I would like to take this opportunity to make an appeal for anyone who was in Sousse, Tunisia around the time of the attack on Friday, 26 June to come forward with information or material that could help with our inquiries. Information can be passed in confidence to the anti-Terrorist hotline on 0800 789 321.

He added:

In the UK, the threat from international terrorism remains severe, meaning an attack is highly likely. Due to this level of threat the police service is already operating at a heightened state of alert and our security plans for public events reflect this readiness.

However, in light of recent events we have reviewed security measures at a number of events and celebrations taking place this weekend. This is not in response to any specific threat but it is right that we keep our security plans under continual review to help protect and reassure the public.

We continue to do everything we can to help keep the people safe by identifying, pursuing and prosecuting suspects and disrupting their activities.

There has been a significant increase in the level of counter terrorist policing activity in the UK. Last year there were over 330 arrests – about one a day – and 89 people were convicted for terror-related offences.

DAC Rowley said:

Specialist officers continue to work with partners to strengthen the protection and security of key sites, business and public places around the UK to help ensure they are safe for visitors and workers.