China firmly opposes the United States' frequent sanctions against some Chinese companies on the basis of its domestic laws, said China's Foreign Ministry spokeswoman Zhang Qiyue Thursday.

Zhang made the remark at a regular press conference when asked to comment on recent US sanctions against four Chinese companies, which the US side accused of selling weapons of mass destruction to Iran.

"China strongly opposes the proliferation of weapons of mass destruction and related means of delivery," Zhang said, adding that

China has established an integral law system on non-proliferation export control, and taken measures to enhance law enforcement in this area.

If authentic evidence is found to prove that Chinese companies or individuals have engaged in illegal export activity, the Chinese government will impose penalty according to law, she said.

The US frequent sanction upon Chinese companies according to its domestic law is not conducive to the effective cooperation between the two countries in the non-proliferation area, she said.