A North Carolina pastor has been sentenced to seven years in prison and fined a hefty charge after he allegedly "organized an illegal border crossing."

According to persecution watchdog China Aid, a court in China's southern Yunnan province handed down the sentence on March 23, one year after Pastor John Cao was detained while engaging in humanitarian work along the China-Burma border.

Officials charged both Cao and his co-worker, a Christian named Jing Ruxia, with "organizing illegal border crossing," even though they have crossed the border many times before with no previous issues.

Cao, a North Carolina pastor well-respected for building 16 schools that service 2,000 impoverished minority children in Myanmar's northern Wa State, will spend the next seven years behind bars and is expected to pay a 20,000 yuan ($3,000 USD) fine.

Jing, who was released after spending a year in custody, received a one-year sentence and a 5,000 yuan (approximately $792.00 USD).

Cao has held U.S. permanent residency since 1990 but kept his Chinese citizenship so that he could continue entering China for his mission work. He pastored a church in Greensboro, N.C. and is married to an American citizen. Cao and his wife have two sons, who still reside in the United States.

World Magazine notes that Cao's problems with Chinese authorities began last year as government scrutiny against Christians intensified. Prior to his arrest, police closed local Chinese Bible schools, questioned his co-workers, and forbade him from speaking at a conference in Hong Kong.

Last year, China Aid president Bob Fu expressed a belief that U.S. President Donald Trump should "loudly urge China to free [Cao]. It will set a bad precedent if China is allowed to deal with Pastor John in this way when he should be awarded for his work," he said.

He warned that in recent years, China has already become an "uncontrollable dragon," and under Chinese President Xi Jinping, the country increasingly resembles the police state in North Korea.

China is listed No. 43 on Open Doors USA's World Watch List, which states that church life is heavily controlled by the government. On February 2, China's amended Regulation on Religious Affairs went into effect, further tightening restrictions on Christian churches and organizations.

Under the new rules, unauthorized groups are also banned from receiving donations, providing religious information online or organizing training related to their religious beliefs.

"We can feel the control getting tighter in recent years," Su Tianfu, a pastor in Guiyang, Guizhou province, who was charged with "leaking state secrets" after his 400-member house church, the biggest in the southwestern province, was forced to shut down in 2015, told the South China Morning Post.

"Other family churches are also under tremendous pressure," Su said. "Some have been forced to close and others are being closely monitored."

Protestant Christianity has been one of the fastest-growing movements in China, with the number of followers estimated at 93 million to 115 million, according to Purdue University scholar Yang Fenggang.