People in Oxfordshire have been told by police to remain 'alert but not alarmed' following the terror threat level being raised, as armed police are deployed in public areas of Oxford.

Last night the Prime Minister said the national threat level had been raised to 'critical' meaning an attack remains highly likely and could be imminent.

Police said there is no intelligence to suggest a specific threat to the Thames Valley but that overnight additional armed and unarmed officers had been deployed in 'key locations' in the county.

They include Oxford's Ashmolean museum, where afmed police have been stationed this lunchtime.

The force said this was focused on crowded places, including transport hubs and shopping centres.

It comes after it was revealed 'intense' discussions are taking place about security for an upcoming music festival in Oxford as authorities react to the Manchester terror attack.

Deputy Chief Constable John Campbell said: "At this time we need everyone to remain alert but not alarmed. 

"We need your help to help us protect our communities and disrupt those who seek to harm us.

"I would urge you to contact the police straight away if you believe that someone is acting suspiciously.

“Our officers and staff will continue to provide a visible presence in our communities and we have the specialist resources in place to respond in an emergency."

Bob Price, leader of Oxford City Council, said changes to the arrangements for Common People this weekend, in South Park, had not been confirmed but organisers were holding discussions with police.

He said wider safety plans for the city had been 're-examined very carefully and authorities were prepared' for major incidents.

But Mr Price also stressed people should not be alarmed.

He said: "We have to accept there is a degree of danger present around the country, but that should not stop us carrying on with our normal lives.

"So it's very important that people do carry on, but they should of course continue to take sensible precuations wherever they are.

"That is why authorities are doing what they are doing. We will always aim to make things as safe as possible.

"What the police are doing is maintaining particular vigilance in places where the public gather."

Mr Price's comments came as thousands of revellers prepare to descend on South Park for Common People on Saturday and Sunday.

Speaking this morning, he added: "At this stage we do not know exactly how they [the arrangements for Common People] will change, but there have been intense discussions between the police and the organisers about the need for extra vigilance.

"It always was going to be quite strong, but I know talks were taking place yesterday about how to make certain there is even less likelihood of any issues."

He said he had not told whether armed officers would be deployed in Oxford.

Police said they would not confirm details of locations, tactics and numbers of officers in order 'to ensure the effectiveness of deployments'.

Monday night's bomb attack on the Manchester Arena killed 22 people, including children, and injured 59 more.

Speaking on Tuesday the Prime Minister also said members of the military will be deployed to guard key sites as part of what is being called Operation Temperer.

Armed forces personnel will be visible at 'big events' such as football matches and concerts, she said.

Prior to the government announcment a spokesman for Common People said: "The safety of our audience is of utmost importance to us.

"The team at Common People are currently in discussions with the police in both Southampton and Oxford and are consulting with our security company to align our strategy for this weekend’s festival.

"Our thoughts are with the families in Manchester affected by this tragedy."

It is the second year the music festival has taken place in Oxford, with organisers expecting it to attract more than 15,000 people.

Headliners are set to include hip-hop artist Sean Paul on Saturday night and Pete Tong on the Sunday, with other acts and performances including Rag’n’Bone Man, Groove Armada, Foals and Becky Hill.