After completing his studies in Australia and securing a prized job as a biomedical researcher, Dr Xianzhong Lau, a 30-year-old Singaporean, was in the process of applying for a work visa when he received "devastating" news.

In a surprise announcement on April 18, Australia's federal government revealed it was tightening the immigration laws for skilled workers.

Dr Lau began applying for a temporary skilled work visa six weeks ago but suddenly found himself no longer eligible.

His profession - life scientist - was one of more than 200 removed from the government's list of in-demand jobs, meaning that he can no longer obtain the visa.

So, despite living and studying for nine years in Melbourne, he has been forced to give up his job and his apartment and to say goodbye to friends. Dr Lau, who just received his PhD completion letter last Thursday, will fly back to Singapore on Sunday, a week before his student visa expires.

"I was shocked and devastated when I found out," he told The Straits Times.

"It is happening really suddenly. I spent my whole adulthood here since 21 - I have settled down, made a solid group of friends."

He added: "I now know Melbourne better than Singapore."

There are currently about 265,000 international students at Australian universities, including about 8,000 from Singapore. Many stay and work after their studies.

The government has kept the 485 visa, which allows many students to work for 18 months after graduating. But the 457 visa has long provided an additional option for those who want to stay longer or have already used a 485 visa.

Dr Lau finished his national service in Singapore and then completed his undergraduate and graduate studies at the University of Melbourne. He used a 485 visa after completing his honours degree.

Since finishing his doctoral work, he has been analysing cell cultures at biopharmaceutical company OccuRx, which is run by one of his thesis supervisors.

He said he now plans to seek research work in Singapore or perhaps abroad.

"I had my mind set on working long term in Australia as a researcher - because of this situation, I can't," he said.

"I am aware that Singapore has opportunities as well and many other countries have similar opportunities. The devastation is moving from a place that you have been in for so long."

Pledging an "Australian first" approach to jobs, the government has abolished the 457 temporary skilled work visa, which was available for up to four years and allowed a path to permanent residency.

Instead, the government has introduced two temporary skilled visas - one lasting two years and another lasting four years. Only those on the longer visa will be able to apply to become permanent residents.

In addition, the list of occupations to which the visa applies has been cut by 216, with 268 occupations available for the two-year visa and 167 for the four-year visa.

A 20-year-old Malaysian, Mr Felix Tan, a second-year law and business student at the Queensland University of Technology, was one of the fortunate ones whose preferred profession - as a lawyer - remained on the list.

He told The Straits Times he was planning to work as a commercial or family lawyer in Australia after he completes his studies. He said he was glad not to be affected, but the changes were a "huge thing" for many international students.

"Personally, I am not affected because my occupation is still on the skills list," he said. "The students who will be affected are mostly studying business degrees and engineering. These are the ones that have been removed."

According to a report in The Australian on April 26, about 6,000 students last year moved to the 457 visa. Another 144,000 stayed using options such as other student visas or the 485 visa.

Universities are hoping the immigration changes will not discourage prospective foreign students. But a tightening of the rules will limit the number of foreign workers. There are currently about 170,000 foreigners and their families who are in Australia on the 457 visa.

Ms Josephine Adriana Prasetya, a 22-year-old Singaporean studying commerce at the University of Sydney, said she will complete her degree at the end of next year and plans to return home to work in marketing.

"I am not really sure about all the changes," she told The Straits Times. "I know Australia has a list of occupations to get the visa. I knew that marketing was not there and that I would be going back to Singapore."