A MASSIVE counter-terrorism operation which began after suicide bomber Salman Abedi detonated an improvised explosive device in Manchester saw 13 arrests made across the north of England and members of Abedi’s family detained in Libya.

Last night eleven people remained in custody following fresh raids in the Cheetham Hill area of Manchester where some streets were evacuated.

Last Monday night British-born Abedi walked into the foyer of Manchester Arena as crowds streamed out of an Ariana Grande concert and detonated a device packed with shrapnel, killing 22 people, including children.

Around midday on Tuesday Ismail Abedi, the Manchester terrorist's 24-year-old brother, was arrested by plain-clothes officers in Whalley Range, south Manchester.

Police simultaneously swooped on Abedi's Fallowfield home, blasting the door off as they began their search. Forensic officers were later seen leaving the building carrying a booklet titled Know Your Chemicals.

The next day several arrests were made, beginning at 10.30am when three men, aged 18, 21 and 24, were arrested, again in Fallowfield, south Manchester.

Armed police then arrested a 33-year-old man carrying a suspicious package in Wigan at 5.30pm, forcing the area to be cordoned off.

Around 8.30pm, in Nuneaton, Warwickshire, a 22-year-old suspect was arrested at gunpoint and led away in a protective forensic suit.

Within 20 minutes police had raided a block of flats in Blackley, north of Manchester city centre, and a 34-year-old woman was arrested. She was later released without charge.

On Wednesday night Libyan authorities announced that Abedi's younger brother Hashim and father Ramadan had been detained.

There was an increase in police activity in the early hours of Thursday, beginning at 1.45am when a controlled explosion was carried out during a search of a property in Moss Side, south of Manchester city centre.

Just after 6am, two men were detained in the Manchester area – a 16-year-old boy in Withington and a 38-year-old in Blackley – in connection with the attack. The teenager was later released.

Again on Thursday morning at 10.45am army bomb experts were sent to the Hulme area of Manchester following reports of a suspicious package, which was deemed safe.

Just after midday Greater Manchester Chief Constable Ian Hopkins hailed the arrests as "significant" and said some of the items seized in raids are "very important".

Around 5.25pm a bomb disposal squad was sent to the house in Withington where the teenager was arrested on Wednesday night.

Then at 7.15pm another bomb disposal team was scrambled to the house belonging to the suspect arrested in Wigan on Wednesday.

In the early hours of Friday morning police arrested a 30-year-old man in Moss Side, while a search was carried out at a property in St Helens, Merseyside.

That night, at 8.10pm, a 44-year-old man was arrested in Rusholme on suspicion of terrorism offences.

Two men, aged 20 and 22, were arrested in the early hours of Saturday morning. Officers blasted a door off a property in Cheetham Hill, near Manchester city centre.

The dawn raid followed searches at a separate address in Cheetham Hill and another in the Longsight area.

At 10.45am yesterday Greater Manchester Police announced an evacuation in an area of Moss Side, where counter-terror police had been searching a property.

The wave of arrests and raids are believed to have closed the net on the terror ring behind the attack, but counter-terror chief Mark Rowley warned "more arrests and more searches" could follow.

He said: "We are getting a greater understanding of the preparation of the bomb. There is still much more to do – there will be more arrests, there will be more searches.

"But the greater clarity and progress has led (Joint Terrorism Analysis Centre), the independent body which assesses threat, to the judgment that an attack is no longer imminent."

Monday night's massacre at the Manchester Arena left 22 dead, including seven children, and scores of others injured – the worst terrorist outrage to hit Britain since the July 7 attacks in 2005.

It led the JTAC to increase the terror threat level to "critical", meaning a further terror attack was considered "imminent". It has now been reduced to "severe", meaning an attack is "highly likely".

Speaking after a meeting of the Government's Cobra emergency committee Prime Minister Theresa May said the decision had been taken after "a significant amount of police activity" over the last 24 hours.

She said: "The public should be clear about what this means – a threat level of severe means an attack is highly likely. The country should remain vigilant."