In a statement, Greater Manchester Police confirmed that 22 people, including children, were killed by a suicide bomber at the Ariana Grande concert at Manchester Arena yesterday.
West Yorkshire Police this morning said officers from the force will be working with police in Manchester today following the attack.
The explosion came as Britain is on a high state of alert for terror attacks following the Westminster atrocity two months ago in which Khalid Masood killed five people before he was shot dead by police.
The official threat level for international terrorism in the UK has now been 'Severe' - indicating an attack is highly likely - for more than two years.
'Severe' is the second highest out of five levels, one below 'Critical' - which means an attack is expected imminently.