Police have confirmed 19 people have been killed, and a further 59 seriously injured, after an explosion at Manchester Arena shortly after the end of a concert by US singer Ariana Grande.
Parents and friends have been searching for loved ones still missing, while local venues have opened up to stranded concertgoers.
Celebrities from around the world have taken to Twitter to express their dismay, including politicians, musicians and athletes.
Former UKIP leader Nigel Farage.
Singer Selena Gomez is a friend of Grande's:
Manchester City captain Vincent Kompany:
Leader of the Labour Party Jeremy Corbyn:
London Mayor Sadiq Khan:
New Zealand singer Lorde:
Canadian Prime Minister Justin Trudeau:
Costa Rican-American actor Harry Shum Jr:
Minority Leader of the US House of Representatives Nancy Pelosi:
Opposition leader Bill Shortern.
'American nationalist' Mike Cernovich.
Australians with concerns about the welfare of family and friends in Manchester should attempt to contact them directly. If you are unable to contact them, call the Department of Foreign Affairs and Trade’s 24-hour Consular Emergency Centre on 1300 555 135 (option 6) or +61 2 6261 3305 if overseas.
A local hotline established by authorities in the UK on 0161 856 9400.