China and Qatar on Thursday signed deals for the purchase of five million tonnes of liquefied natural gas (LNG) a year from the oil-rich Gulf state, the two sides said.

PetroChina, the listed arm of China's largest oil and gas producer, signed a deal in Beijing with Qatargas and Shell under which the Chinese firm would buy three million tonnes of Qatari LNG per year for 25 years, according to a statement issued by the companies.

"I am proud that ... Qatar will be able to supply cleaner energy to contribute to the Chinese success story and China will be able to contribute to Qatari success as a customer for our natural resources," Abdullah bin Hamad Al-Attiyah, Qatar's energy minister, said in the statement.

In the other deal, China's largest offshore oil producer, CNOOC, and Qatargas signed an agreement involving shipments of two million tonnes of LNG per year, according to another statement issued by both sides.

"We see Qatar, the world's leading LNG producer, as a reliable partner in meeting our long term energy needs," CNOOC President Fu Chengyu said in the statement. "The cleaner energy from LNG will contribute to fuelling China's fast economic development."

The time-frame for the CNOOC deal was not given, and no financial details of either deal were disclosed.

The agreements were signed during a visit by Sheikh Hamad bin Jassem al-Thani, who met with Chinese President Hu Jintao on Thursday.

Energy-hungry China, eager to fuel its booming economy, began importing natural gas in 2006, receiving its first shipment of LNG from Australia's Northwest Shelf fields.

The Chinese-Australian deal, set to last 25 years, was worth about 25 billion Australian dollars (23.3 billion US dollars).

That same year, Malaysia's state-owned Petronas agreed to provide, for a period of 25 years, more than three million cubic metres of LNG per year to China's Shanghai LNG Company, in a deal valued at 25 billion dollars.

Qatar has the world's third-largest gas reserves, after Russia and Iran.