Security guards have been blocking access to the AIBA offices in Lausanne.
A notice pinned to the door and signed by an interim executive committee said that a motion of no confidence had been called against Taiwan's Wu.
AIBA, which organises amateur boxing including Olympic competitions, has been struggling with instability and financial difficulties.
In a statement issued on Tuesday, AIBA had said that an extraordinary congress would be held within the next three months.
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"In addition, motions were passed enabling the establishment of an interim management commitee (IMC) to manage the work of AIBA and AIBA headquarters and the organisation of the extraordinary congress.
"Consequently in this moment of transition it has been decided to close the office for the remainder of this week. The staff are being offered these three days as holidays."
Wu, who has been head of the federation since 2006, is blamed for causing financial irregularities by his opponents, who believe AIBA is on the brink of bankruptcy.