China hit the US with final anti-dumping and anti-subsidy duties on imports of solar-grade polysilicon on Monday, as ­Chinese producers "suffered substantial harm" due to US subsidies and cheap products.

The anti-dumping duties, announced by the Ministry of Commerce (MOFCOM), were in line with initial levels levied last year of up to 57 percent on imports of the raw material used to make solar panels.

Anti-subsidy duties on US imports were set at 2.1 percent, lower than the upper limit 6.5 percent preliminary duties set in September 2013, according to MOFCOM.

The ministry also levied final anti-dumping duties on South Korean polysilicon of between 2.4 percent and 12.3 percent.

An investigation ­concluded that China's producers ­"suffered substantial harm" due to the US and South Korea selling below cost in the ­Chinese markets, and also due to US subsidies, the MOFCOM said in statements on its website.

The duties would be effective immediately and last five years, the ministry said.

US manufacturers REC ­Solar Grade Silicon LLC and AE Polysilicon Corp were among the hardest hit with anti-dumping duties at 57 percent.

Washington had called previously announced duties disappointing, and many in the US solar industry saw the MOFCOM's move as an attempt to protect China's struggling domestic firms.

The US has already imposed its own duties of about 30 percent on Chinese solar panels in a case finalized in 2012.

China and the European Union have also soured their relations over solar industry disputes.

Europe had planned to ­impose heavy tariffs on ­Chinese solar panels but a majority of EU governments led by ­Germany opposed the plan and sealed a compromise deal in July 2013.

Chinese solar equipment producers like LDK Solar Co Ltd are struggling. China's State Council has pledged to boost support as the government seeks to revive a sector struggling with overcapacity and falling prices.

China aimed to more than quadruple solar power genera­ting capacity to 35 gigawatts by 2015 in an apparent bid to ease a glut in the domestic solar power industry, according to a statement released by the State Council in July 2013.

The Ministry of Industry and Information Technology is implementing the July directive by supporting consolidation in the industry, drafting guidelines for mergers and acquisitions and promoting ­standardization, the State Council said in another statement released earlier this month.