China on Friday opposed unilateral sanctions on North Korea by Washington, a day after the US House of Representatives approved a law granting more power to the executive to take such a step.

"China firmly opposes any country's imposition of unilateral sanctions on any other country according to their own domestic law," Chinese Foreign Ministry spokesperson Geng Shuang said.

Geng described the situation on the Korean peninsula as "very complex and tense" and called for restraint to prevent a major conflict from breaking out, Efe news reported.

On Thursday, the lower house of the US Congress approved a law conferring more power on President Donald Trump to impose sanctions on North Korea and the companies of any country that sell materials to Pyongyang which allow it to develop its nuclear and missile programmes.

The bill, which will go to the Senate for final approval, prohibits North Korean ships or those from any other country, including China, that refuse to comply with the resolutions of the UN Security Council condemning the ballistic missile launches from operating in US waters or docking at US ports.

Geng added that Beijing fully complies with these resolutions despite doubts surrounding China's actions with regards to North Korea.

Although China has publicly distanced itself from Pyongyang and insists it has halted coal imports, some experts believe the two countries are still trading through the "livelihood purposes" clause that allows trade to ensure the survival of the North Korean people.