David Cameron has pledged a "full spectrum" response to terrorists as the British death toll from the Tunisian beach massacre is expected to reach at least 30.

The Prime Minister said Home Secretary Theresa May is travelling to the country today for talks on how to address the extremist threat and to pay condolences at the scene.

An RAF C17 transport plane is also being deployed to help bring stranded tourists home, and potentially repatriate bodies.

Mr Cameron said the Government is working "as fast as we can" to give families information.

"I know it has taken time but these are very difficult things and we must get them right," he told BBC Radio 4's Today programme.

Mr Cameron said the Government was ready to repatriate victims' bodies if requested by their families.

"We are very happy to look at that. There are all sorts of other arrangements being put in place but I am keen that, as a nation, we show respect and our condolences ... and if they would like for us to try and bring back the bodies of their loved ones with dignity and respect that is something we can do."

The Prime Minister renewed his appeal for an end to the use of the name Islamic State.

"I wish the BBC would stop calling it 'Islamic State' because it is not an Islamic state.

"What it is is an appalling barbarous regime that is a perversion of the religion of Islam and many Muslims listening to this programme will recoil every time they hear the words.

"'So-called' or Isil is better," he said - using the abbreviation of the title Islamic State of Iraq and the Levant.

He said the "poisonous death cult" was "seducing too many young minds in Europe, in America, in the Middle East and elsewhere and this is going to be the struggle of our generation and we have to fight it with everything we can."

A total of 38 people were killed when a gunman opened fire on a beach in the Sousse resort on Friday, with the the Foreign Office already confirming 15 of them were from Britain.

However, that number is likely to rise dramatically as more of the victims are identified. Three Irish nationals are also among the dead.

Mr Cameron, who is chairing another meeting of the government's Cobra emergency committee later, said Mrs May and Foreign Office minister Tobias Ellwood would be visiting the resort.

"This is an absolutely horrific attack and I know it has shocked the whole of the country, it has shocked the whole of the world," he said.

Asked if British Muslims had not been tough enough in condemning such acts of terrorism, Mr Cameron said: "No, I don't believe that is the case... the point I am making is there are some organisations and some people who buy not the terrorism, but they buy a lot of the extremist narrative. To those people we have got to say that is not an acceptable view.

"We are not going to engage with people who believe there ought to be a caliphate and women should be subjugated.

"My point is some organisations set themselves up as representative of Muslim communities when actually they are not. Do not treat them as spokespeople for all of the community."