People have been allowed back into Parliament House in Sydney following an evacuation that police say was sparked by the discovery of a suspicious item nearby.

Officers were called to Hospital Road at the back of the Macquarie Street complex at about 10am.

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People inside Parliament House were earlier told to move to the other side of The Domain, which is several hundred metres away.

But workers have since been told the police operation is over and they can now go back into the building.

An announcement broadcast over loudspeakers said there had been a security incident on the concourse between Parliament House and the State Library.