London City Airport advised all passengers due to travel Monday not to go to the airport, and instead contact their airline for further information.
The ordnance was discovered in King George V Dock, close to the runway of London's most central airport, during planned works.
As the World War II bomb was found near London City Airport on River Thames, the airport was closed on Sunday.
"The airport is cooperating fully with the Met Police, Royal Navy and London Borough of Newham", the airport's statement added.
It's not yet publicly known what type of bomb it is, nor when the airport will reopen.
Specialist officers and the Royal Navy confirmed the device was explosive and the airport was shut at 22:00.
'The operation to remove the ordnance is ongoing in partnership with our colleagues in the Royal Navy.
The Metropolitan Police said the discovery was reported before dawn on Sunday, at around 0500 GMT, and the exclusion zone was put in place at 2200 GMT.
The London City Airport is an worldwide airport located in the Newham Borough of East London.
Some flights in and out of the airport will be affected.
The transport authority wrote: 'The airport has been closed due to an emergency services incident. Surrounding roads have also been closed. Traffic is light in the area'.