A priest and a Catholic human rights activist have reportedly been prohibited by the Vietnamese government from leaving the country due to "national security" reasons.

Fr. Joseph Dinh Huu Thoai, who belongs to an order commonly known as the Redemptionists, was reportedly planning to visit family and friends in the U.S., but was prevented from doing so by army officers earlier this month.

When Thoai asked the officers why he was prevented from leaving the country, they insisted that they were only following orders handed down to them by their superiors. The priest has contended he has not broken any laws and that he had not been listed on any police ban order.

Thoai, who has been outspoken about human rights abuses in Vietnam, has accused the government of depriving citizens of their freedom to travel. The Redemptionist priest had been banned from traveling to Cambodia in 2011, according to UCA News. He noted that he had been allowed to leave the country back in November.

Earlier this month, Vietnamese authorities also prevented Maria Do Thi Minh Hanh from traveling to Germany.

Hanh, the president of the civil society Viet Labor Movement, was supposed to visit her mother in Germany, but officials stopped her at Tan Son Nhat International Airport in Ho Chi Minh City, saying she was not allowed to leave the country for "national security" reasons.

The activist claimed that the government had previously vowed to German officials that she would be allowed to leave the country.

"The government tricked the German government and me when they allowed me to go to Cambodia, but have now barred me from travelling to Germany," Hanh said, according to UCA News.

The incident at Tan Son Nhat International Airport was reportedly the fourth time that Hanh was barred from traveling to other countries. In 2010, Hanh was arrested for "disrupting security" and later sentenced to seven years in prison, but was subsequently released in 2014.

The Vietnamese government has been known to hand down lengthy jail sentences to Christian pro-democracy activists. Last month, the People's Court of Hanoi sentenced Christian lawyer Nguyen Van Dai to 15 years in jail after he was convicted of attempting to overthrow the communist government.

The court also sentenced Pastor Nguyen Trung Ton and journalist Truong Minh Duc to 12 years each on the same charges. Activist Nguyen Bac Truyen was sentenced to 11 years, while Pham Van Troi was sentenced to 11 years. Le Thu Ha, an assistant of Dai, was sentenced to nine years.

In addition to the jail sentences, the defendants were also sentenced to house arrest ranging from one to five years in length.