Following a preliminary investigation, the Taiwan region's restrictions on products from the Chinese mainland are suspected of violating World Trade Organization (WTO) rules, China's Ministry of Commerce (MOC) said on Thursday.

It is suspected that the restrictions are in violation of WTO rules such as those dictating non-discrimination and the general elimination of quantitative restrictions, MOC spokesperson Shu Jueting said at a press conference.

The MOC launched the investigation on April 12 after a trade barrier investigation request was submitted by three mainland import and export trade chambers in March.

The investigation continues through surveys and field research, and it follows the principles of legal compliance, openness, fairness and impartiality, Shu said.

The mainland has urged the Taiwan region to effectively fulfill its WTO commitments, but it has failed to make due changes, she said.

The number of prohibited import items from the mainland has been expanding, with products involved in the investigation growing from 2,455 when the request was filed to 2,509 at present, according to the MOC.

The restrictions have impacted the mainland's petrochemical, textile, electromechanical equipment and automobile sectors, among others, and many quality and affordable agricultural products and daily necessities from the mainland can not be exported to Taiwan, hurting the interests of related export enterprises, Shu said.

The enterprises and trade associations that took part in the investigation have called on the Taiwan region to lift its restrictions, she said.

The trade barrier investigation will continue, and its results will be released at an appropriate time, she said.