The flags are flying at half mast outside Worthing Town Hall "as a mark of respect" following the Manchester attack.
Twenty-two people are reported to have died, with 59 injured following the devastating attack at Manchester Arena last night (May 22).
Alex Harman, mayor of Worthing, was among those to offer their sympathies.
Mr Harman said: "My thoughts are with everyone affected by the atrocity in Manchester.
"We are flying our flags at half-mast as a mark of respect after this terrible attack on so many innocent people."
Councillor Dan Humphreys, leader of Worthing Borough Council, said: "On behalf of the people of Worthing, I'd like to offer my deepest sympathies to the victims and families and all those affected by the horrific attack in Manchester last night."