The main political parties in south west Hertfordshire have all suspended general election campaigning after the fatal bombing in Manchester.

The Watford Observer has also taken the decision to postpone the hustings event due to be held at Watford Grammar School tonight.

Prime Minister Theresa May will chair an emergency Cobra meeting in London into the suspected terror attack at the Ariana Grande concert, which left 22 dead and more than 50 injured.

SEE ALSO: 19 people die in suspected terror attack at Ariana Grande concert at Manchester Arena

Mrs May, Labour leader Jeremy Corbyn and other senior politicians have all expressed their horror at the attack.

Conservative's parliamentary candidate Richard Harrington said: ""I'm shocked and saddened by the horrific attack in Manchester last night.

"My thoughts and prayers are with the victims and their family and friends, as well as with the people of Manchester.

"I would also like to take this opportunity to pay tribute to our fantastic emergency services who have been helping all night and this morning. " 

The SNP has postponed the launch of its manifesto which was due on Tuesday.

The Lib Dems, UKIP, Green Party and Plaid Cymru have also announced that they will be ceasing campaigning until further notice.

Chris Ostrowski, Labour's parliamentary candidate for Watford, said: "The cowardly and barbaric attack in Manchester is a ghastly turn of events, and my thoughts and prayers are with the families of the loved ones who have been killed and injured.

"We must not allow terrorism to derail our way of life, and we stand united with Manchester."

Union flags are being lowered to half mast in Downing Street as a mark of respect.