Around 12 million tickets for next year's Expo have been sold by Sunday since March, beating this year's 10 million target expected by the organizer.

About 90 percent of sales come from Yangtze River Delta cities, Chen Xianjin, deputy director general of the Bureau of Shanghai World Expo Coordination, revealed on Sunday. The delta region comprises Shanghai and neighboring Jiangsu and Zhejiang provinces.

"We have also witnessed continuous increase in ticket sales from other parts of China, which signals that the Expo has warmed up across the host country," said Chen.

He attributed the recent sales boom to discounts. The current price for a standard day admission is 140 yuan ($20.53) with a 20-yuan discount, which will cost 150 yuan next year before the opening in May.