The celebration, said to be the largest celebration of the anniversary held on the mainland, is co-organized by the Shenzhen government and the HKSAR government.

Participants include 5,000 Shenzhen-based university students and about 5,200 Hong Kong youths from 115 organizations and communities, of whom 1,000 are on their first trip to Shenzhen.

Most of the young people from Hong Kong came by bus through the newly-inaugurated Shenzhen Bay Port (or Hong Kong-Shenzhen Western Corridor), the fourth border crossing for vehicles between Shenzhen and Hong Kong.

They will visit the city museum, universities and high-tech districts, attend forums and perform hiphop dances, karate, sword play and fashion shows.

Later Sunday, they will go to a gala attended by celebrities from Hong Kong and the mainland.

In Hong Kong and the mainland, celebrations are being held to mark the 10th anniversary of Hong Kong's return. In Harbin, capital of northeast China's Heilongjiang Province, residents displayed a 1,000-metre-long painting to mark the occasion.

Sunday's celebrations in Hong Kong began with a flag-raising ceremony, attended by more than 1,000 people, including Chief Executive Donald Tsang, and will end with a grand fireworks display in the evening.