China has agreed to buy 24 fighter jets and four submarines from Russia, Chinese state media report.
It is reported to be the first time in a decade that China has made a large-scale military purchase from Russia.
Two of the submarines will be built in Russia and two in China.
The deal, signed just before last weekend’s visit to Moscow by the Chinese President, Xi Jinping, comes as both sides increase military co-operation.
Correspondents say Moscow and Beijing are trying to counterbalance what they see as American military dominance.
China is buying 24 Su-35 fighters and four Lada-class submarines, reported the Communist Party organ the People’s Daily and China Central Television (CCTV).
They did not put a value on the purchases.
China’s official defence budget rose by 11.2% in 2012 – pushing it above $100bn (£65bn) for the first time. But foreign experts have estimated that Beijing’s actual military spending could be as much as double the official budget.
US defence spending was reported as standing at more than $700bn.
Beijing – which is also embroiled in a bitter row over disputed islands with Japan – launched its first aircraft carrier last year.
“The Su-35 fighters can effectively reduce pressure on China’s air defence before Chinese-made stealth fighters come online,” the People’s Daily was quoted as saying.
It said the two countries were expected to co-operate further in developing military technology – including for S-400 long-range anti-aircraft missiles, 117S large thrust engines, IL-476 large transport aircraft and IL-78 aerial tankers.
Chinese President Xi Jinping visited Moscow from Friday to Sunday for talks with his Russian counterpart, Vladimir Putin – his first trip abroad since becoming head of state earlier this month.
The two countries are also pursuing a number of deals for Russia to supply Chinese industry with oil and liquefied natural gas.
President Xi’s visit was lauded by the state-run China Daily as a “well-deserved riposte to Washington for America’s military ‘pivot’ to Asia. Xi is executing China’s own ‘pivot’ – the visit to Moscow to cement ties with” Mr Putin, the paper said.
“Xi’s decision to make Moscow the destination of his first official visit as China’s president will give the US a sharp reminder that it is not the only power able to flex its muscles,” the report, translated by BBC Monitoring, went on.