China on Tuesday rejected a U.S. computer security firm's accusation of Chinese hacking against European countries before the G20 Summit in September.

According to recent media reports quoting research by FireEye Inc., Chinese hackers infiltrated the computer networks of five European foreign ministries by sending emails containing tainted files to staff.

"U.S. computer security firms have been keen on playing up the so-called cyber threat from China. But their so-called evidence is never solid but widely doubted by professionals," Foreign Ministry spokesman Hong Lei said at a daily news briefing.

"They are trying to gain attention with fake facts, which will neither be conducive to international cyber security cooperation nor the professional qualifications and reputation of the firms involved," Hong said.

He reiterated that China will firmly safeguard cyber security and oppose hacking in all forms.

China has formulated laws to combat such behavior and is also working with the international community on tackling cyber crimes, the spokesman added.