Manchester terror attack probe widens as police angered by US leaks

UK police raced to close down a network around the Manchester suicide bomber on Thursday, as a row escalated between London and Washington over material from the probe leaked to US media.

British-born Salman Abedi, 22, who was known to security services, killed 22 people at a concert venue packed with children on Monday when he bloew himself up at the end of a concert by US pop singer Ariana Grande.

Authorities believe he had help in building the bomb, which photographs published by the New York Times showed was sophisticated and powerful, and that his accomplices could be ready to strike again.

Manchester police arrested five men and one woman on Wednesday, bringing the total held for questioning to seven. Abedi’s father and brother were among those arrested, having been detained in Libya.

"I spoke to [Salman Abedi] about five days ago ... there was nothing wrong, everything was normal," Ramadan Abedi told Reuters news agency, moments before he was arrested.

A spokesman for the local counter-terrorism force said his brother Hashem Abedi was arrested on suspicion of links with Islamic State and was suspected of planning to carry out an attack in the Libyan capital.

The first arrest made in Britain on Tuesday was reported by British and US media to be Abedi's older brother.

Police also searched multiple addresses in northern and central England.

Explosives were found at one site, the Independent reported, citing security service sources.

"I think it's very clear that this is a network that we are investigating," police chief Ian Hopkins said outside Manchester police headquarters.

"And as I've said, it continues at a pace. There's extensive investigations going on and activity taking place across Greater Manchester as we speak."

Authorities in Britain have become increasingly angered by US leaks from the investigation, including the bomber's name on Tuesday and the photos of blood-stained fragments from the bomb on Wednesday.

"We are furious. This is completely unacceptable," a government ministry source said of the images "leaked from inside the US system".

British police chiefs said the breaches of trust between security service partners were undermining their efforts.

British Prime Minster Theresa May will meet US President Donald Trump at a NATO summit in Brussels on Thursday, but officials said she would cut short the second leg of her trip to the G7 summit in Italy.