BEIJING – China is trying to punish ally North Korea for its nuclear and missile tests, stepping up inspections of North Korean-bound cargo.

The move appears to be a calculated effort to send a message of Chinese pique without further provoking a testy Pyongyang government.

Freight handlers and trading companies at ports and cities located near the North Korean border are complaining about more rigorous inspections and surprise checks that are raising the costs of doing business with the often unpredictable North Korea.

Machinery, luxury goods and daily necessities such as rice and cooking oil are among the targeted products, the companies said, and business is suffering.

An executive with Dalian Fast International Logistics Co. in the northeastern port city of Dalian, across the Yellow Sea from the North Korean port of Nampo, said the company’s business is off by as much as 20 percent this year.