Islamic State's claim it is behind the Manchester bombing has not been verified in the United States, intelligence chiefs have said.

The terror organisation, known as IS and Isis, claims responsibility for "virtually every attack", US director of national intelligence Dan Coats said.

He told the senate armed services committee the atrocity was "tragic" and a reminder of the real threat faced by the West and its allies.

Mr Coats said: "Isis has claimed responsibility for the attack in Manchester, although they claim responsibility for virtually every attack.

"We have not verified yet the connection."

Mr Coats said he had just returned to the US after a visit to London where he met intelligence counterparts.

"We spent a significant amount of time discussing threats to our respective homelands.

"It's a tragic situation that we see all too much of in countries around the world, particularly our allies.

"Once again, it reminds us that this threat is real, it is not going away and needs significant attention to do everything we can to protect our people from these kinds of attacks."

Committee chairman senator John McCain said the "horrific" attacks showed the "world is on fire".

He said: "Last night's horrific attack on Manchester was a gruesome reminder that the world is on fire.

"Everywhere we turn we can sees threats to the world's rules-based order that underpins global security and prosperity.

"Yet when it comes to the great national security challenges we face, US policy and strategy are consistently lacking.

"Whether it's China, Russia, North Korea, Iran or radical Islamist terrorism I have heard few compelling answers about how the United States intends to use its alliances, its trades, its diplomacy, its values but most of all its military to protect and defend our national interests and the rules-based order that supports them."

The Republican senator pressed Mr Coats on whether the "tragedy" in Manchester should add urgency to efforts to re-taking Raqqa, the Isis-held stronghold in Syria.

Mr Coats replied: "Well, that won't solve the problem, particularly the home-grown and inspired attacks.

"Clearly going to the heart of Isis and driving a stake through that heart, we assess, will significantly improve the situation.

"The plotting and the planning that comes from a centralised caliphate or safe haven for Isis, we have seen the damage that's occurred.

"We do assess, however, that its ideology and methods have spread like tentacles into many places, most of them ungoverned countries, and sent some foreign fighters back home that might want to carry on their mission."

Mr Coats said his counterparts in London were most concerned about "inspired or home-grown violent extremist attacks", which are the most difficult to prevent.

He told the committee: "Initial reports that we have received are that it was indeed a suicide attack.

"Whether there were others involved in that is under assessment."