Historical documents on display in Taipei show Taiwan's ruling Kuomintang (KMT) party owes late Chinese communist leader Mao Zedong money from a brief period nearly 90 years ago when he was a member.

"The KMT failed to pay the salary to Mao and a number of other party members over a three-month period in 1924 when it was struggling financially," Shao Ming-huang, the head of KMT Party Archives, told AFP Tuesday.

The nationalist KMT was China's ruling party for two decades until it lost a civil war to its communist rivals led by Mao in 1949, and was driven into exile on Taiwan.

In the early 1920s Mao, already a dedicated communist, was elected to the KMT's central committee and became an executive of the party's Shanghai branch.

It was part of a strategy under which the KMT and the communists agreed to shelve their differences and cooperate to defeat local strongmen in order to unify China.

As the Shanghai branch chief, Mao was supposed to receive 120 silver coins a month.

"I cannot give a rough equivalent in today's money. But I'm sure it was good pay at the time, about the salary levels of college professors then," Shao said.

The payroll receipts and other historical documents involving senior Chinese officials, such as late premier Zhou Enlai, have been on display during an exhibition on the KMT's history at party headquarters in Taipei.

The documents have drawn thousands of Chinese tourists to visit the island, Shao said.

Taiwan has been governed separately since the KMT fled to the island in 1949. But China still considers it part of its territory awaiting reunification, by force if necessary.

However, ties have improved markedly since 2008 when President Ma Ying-jeou of the KMT came to power in 2008 on a platform of ramping up trade and tourism links.