Hundreds of Chinese students in the United States face visa cancellation and deportation after a sting operation by the US Department of Homeland Security to catch agencies promoting fake universities and help the students get visas illegally, China Central Television reported on Wednesday.

More than 20 agencies were caught. More than 1,000 students in the US, mainly from China and India, now face visa cancellation and deportation.

US authorities announced last week that they had set up a fake university three years ago - the so-called University of Northern New Jersey. The sham school had no teaching or administrative staff, and no educational activities had ever taken place, CCTV reported, citing a federal prosecutor.

A Chinese student, surnamed Zhang, said he didn't know the school was fake and couldn't believe that he and hundreds of peers had been tricked by the US authorities.

Deng Hong, a lawyer hired by some Chinese students to deal with the incident, told CCTV that many students who wanted to remain in the US after the expiration of their legal student visa were implicated.

Foreign students who want to stay in the US typically need to switch from a student visa to an H1B classification that allows for employment. But competition is fierce. At least 250,000 international students participated in a lottery for 80,000 H1B visas that ended in early April, Deng said.

Rising numbers of international students, especially Chinese, go to the US to study. The annual Open Doors Report released by the Institute of International Education showed that in the 2014-15 academic year, nearly 1 million students from around the world were studying in the US. Of those, about 304,000 - the largest group - were Chinese.

Given the stiff competition, students with expiring visas who fail to get an H1B in the lottery had no choice, Deng said, but to pay an agency about 10,000 yuan ($1,500) and hope that it would find schools they could enrol in so they could remain in the US.

With a fake school, no studies are required, although certificates may be issued.

Lu Weiwei, a staff member at the Chinese Service Center for Scholarly Exchange, said students should be more cautious when choosing universities and agencies overseas.

They should choose one recognized by the ministry, which posts a list online at jsj.edu.cn.