Opponents of a Chinese company's planned interoceanic canal across Nicaragua say police have set up roadblocks and are harassing demonstrators heading to a Wednesday protest in the nation's capital.

The National Council in Defense of the Land, Lake and Sovereignty says police have threatened drivers, seized vehicles and roughed up opponents.

The government hasn't commented.

Critics say the canal proposal threatens to displace rural communities and damage the environment. The 171-mile (276-kilometer) waterway between the Caribbean Sea and Pacific Ocean is to pass through Lake Nicaragua. About 7,000 families living along the route face displacement.

The government says the $50 billion canal will create 50,000 jobs.

The march Wednesday would be the fifth demonstration against the canal concession granted in 2014 to a Chinese company, which has barely broken ground.