The pages, whose signatories include then US vice president George H.W. Bush, the last Soviet leader Mikhail Gorbachev, late Palestinian leader Yasser Arafat and Zimbabwean President Robert Mugabe, are apparently up for auction in Spain this week.
The documents were posthumous tributes to Tito, who led socialist Yugoslavia from the end of World War II until his death in 1980. They were written into tribute books during official visits by the leaders to Yugoslavia in the years that followed.
Following a media report that the autographs had been stolen, Belgrade's Museum of Yugoslav History launched an internal probe and established that the pages were missing from the tribute books that were on display in a mausoleum that is part of the museum's complex.
"We reported the case to police and they will inform Interpol... We are waiting for a response," museum official Ana Radic told AFP.
The theft appears to have taken place before the museum took over the running of the mausoleum in 2015, she explained.
"We also contacted the auction house and asked them to cancel the auction and provide us with additional information on the documents so we can confirm their authenticity" and recover them, Radic said.
The auction in Malaga is scheduled for June 3rd.
The director of the British-based auction house said a colleague managing the sale "has been in touch with the relevant authorities and is complying with their requests for further information regarding the documents".
"In the rare event that the ownership of documents is brought into question then we are always willing to assist the relevant parties in further investigations and, if necessary, withdraw documents from the auction until the rightful owner can be established," Richard Davie of Autograph Auctions told AFP by email, without elaborating.
Among the other autographs that have gone missing are those of India's first female prime minister Indira Gandhi, assassinated Swedish premier Olof Palme, Cambodia's king Norodom Sihanouk, late Syrian president Hafez al-Assad and Romanian communist dictator Nicolae Ceausescu.
A decade after Tito's death, federal Yugoslavia fell apart in a series of bloody wars, with its former republics emerging as independent states in the western Balkans.
By Katarina Subasic / AFP