China and Afghanistan have signed a range of security and economic agreements during a visit to Kabul by top Chinese official Zhou Yongkang.
China's domestic security chief, is the most senior Chinese official to visit the country for almost 50 years.
One of the agreements involves China helping train the Afghan police force.
Afghan neighbours are seeking to expand their influence in the country ahead of the pullout of US-led troops from the country in 2014, analysts say.
China wants to increase investments in Afghanistan's resources sector.
In June this year, the two countries decided to upgrade their ties to the level of a strategic and co-operative partnership at a regional conference in the Chinese capital Beijing.
For security reasons, details of Saturday's visit by Mr Zhou - which included a meeting with Afghan President Hamid Karzai - were kept secret until he had left the country, the BBC's Ethirajan Anbarasan reports from Kabul.
Under the new agreements, around 300 Afghan police officers will be sent to China for training over the next four years, an Afghan foreign ministry official told the BBC.
China has been investing in Afghanistan's mineral sector for several years, as it searches for mineral resources in different parts of the world.
A Chinese state-owned mining company has invested in a copper mine in the eastern province of Logar, although work to excavate a 7th-Century Buddhist site has slowed work on the mine.
Last year, China also won approval for oil exploration and extraction in the Amu Darya river basin.