Written by By Steve McAnon, CNN Singapore

Singapore tightened rules for returning Chinese nationals that could affect up to 45,000 people, according to a top foreign affairs official.

"It was a little unusual from our point of view," Yuen Pau Woo, president of the Singapore Civil Society Network, told CNN, explaining that the government was worried that some returning citizens could travel to North Korea.

"One of the fears is that after they've arrived in Singapore, they're going to go to North Korea to visit, and then before long this space will be taken up by returning Chinese who will seek a [type of] asylum," Woo said.

Yuen Pau Woo, the president of the Singapore Civil Society Network, talks to CNN's Kate Bolduan in Singapore. Credit: Kevin Mazur/Getty Images AsiaPac/Getty Images

On Friday, the Singapore Cabinet published a new notification, requiring people planning to travel from China to visit North Korea and other countries to seek a permit to enter Singapore.

The period, however, for applying for a permit will be a month less than the one allowed to travel to North Korea.

"By extending the permit period, we hope to facilitate more people to travel to the island, and the government will monitor the situation in North Korea," said Wee Leng Meng, the director-general of the Ministry of Foreign Affairs, in a press release Friday.

More or less?

This move could complicate a travel plan the likes of which have never been seen for Singapore citizens, who were often required to apply for a visa upon arrival.

In recent months, North Korea has held several high-profile visits to the city-state, indicating that the latter remains a popular refuge for people who are trying to escape the communist country. In January, Kim Yo Jong, one of North Korea's most powerful women, made a public visit to the island to attend the funeral of former leader Kim Jong Il.

Pyongyang often brands North Koreans who travel to South Korea as "traitors." Uncomfortable stories of illegal ways of crossing the border, like using tunnels or taking boats to hide on the other side, abound among Singaporeans, who note that foreigners are mostly not punished for entering the country without a permit.

People wait in line to cross the border from South Korea to North Korea at the Yalu River in Paju, North Korea on June 10, 2016. (Peter Parks/AFP/Getty Images)

Still, there are concerns about the safety of those who are willing to take a chance on the south.

"There are cases when a certain group of people have managed to go to Korea, to escape to South Korea. And they've been brought back and subjected to torture and illegal arrest and detention. And some of them have been killed," Woo said.

Woo, a Chinese-born Singaporean, described foreign countries allowing North Koreans into their nations without permission as a "game of space."