SHANGHAI, April 30 (Xinhua) -- Chinese President Hu Jintao declared the opening of the World Expo 2010 in the Expo Culture Center in Shanghai Friday evening.

Hu's announcement was echoed by thunderous cheers from spectators in the seashell-shaped venue at the Expo park, which spreads across 5.28 square kilometers along both sides of the Huangpu River.

Among the spectators, French President Nicolas Sarkozy and Republic of Korea President Lee Myung-bak were in attendance along with other world leaders, including Mongolian President Tsakhia Elbegdorj and European Commission President Jose Manuel Barroso.

The Shanghai World Expo, carrying the theme of "Better City, Better Life", will lead new lifestyles, promote harmony between man and nature as well as the overall development of human beings, Chinese Vice Premier Wang Qishan said while addressing the opening ceremony.

International Exhibitions Bureau President Jean-Pierre Lafon said he hoped the Shanghai World Expo would contribute to a social awakening so that cities may become more sustainable, fairer, safer and more harmonious.

It was the first time for the 159-year-old World Expo to be held in a developing country since the inaugural fair in London in 1851.

China has been preparing for the event since Shanghai won its bid to host the World Expo 2010 eight years ago. It is another grand event for the country after the successful Beijing Olympics in 2008.

From the United States to Republic of Korea, a total of 189 countries would present their best at the six-month event, which is expected to attract 70 million visitors from China and abroad and likely to be the largest World Expo ever.