President Hu Jintao on Friday called on Chinese aerospace workers to continue their fine work with the implementation of the nation's key space programmes.

In a congratulatory letter to a Beijing conference marking the 50th anniversary of the nation's aerospace industry, Hu said the industry was a significant symbol of China's strength.

The industry promises great prospects as the nation continues to build a socialist society with Chinese characteristics, he said.

Over the past half century, Chinese space workers have established a complete research system in the aerospace industry.

Their achievements, including developing atomic bomb, missiles, satellites and staging manned space flights, have helped shore up the country's economic, technological and national defence strength, and added to national cohesion, the president said.

He urged workers to concentrate on doing a good job and pushing ahead with the country's key space projects.

The projects include manned space flights, lunar exploration, high-resolution Earth observation and building the next generation of rockets, according to a policy document released by the State Council Information Office on Thursday.

Speaking at Friday's meeting, Premier Wen Jiabao said the development of China's aerospace industry had been based on self-reliance and innovation.

He asked Chinese scientists and engineers to form an innovation system for space science and technology and acquire more intellectual property rights in key space areas.

Wen also called for more international exchanges and co-operation in aerospace development.

China has signed 16 international space co-operation deals and memorandums with 13 countries, space agencies and international organizations over the past five years.

The country will prioritize collaborations in such areas as astronomy research, space physics, micro-gravity science, space life science, lunar exploration and planetary exploration, space officials said.

China began developing space technology in 1956, when the country opened its first institute for missile and rocket research, the No 5 Research Institute attached to the Ministry of National Defence, with scientist Qian Xuesen as its first director.

The country launched its first manned spacecraft, Shenzhou V, into orbit in October 2003, making it the third nation after the former Soviet Union and the United States to send a man into space.

The Shenzhou VI manned spacecraft completed a five-day flight in October last year with two astronauts on board.

It was the first time Chinese astronauts had engaged in experiments in space, another major achievement in the sphere of manned space flight.