Malaysian activists said on Friday they had filed a court challenge to block a rare earths plant being built by Australian miner Lynas, which has stoked fears over radiation pollution.

Activist group Stop Lynas Coalition filed a petition on behalf of residents of eastern Malaysia, where the plant is located, the group's advisor, opposition lawmaker Fuziah Salleh said.

The filing with a court in the capital Kuala Lumpur seeks a review of the government's decision earlier this month to award Lynas an operating license, she said.

Lynas intends to process rare earths -- elements used in such products as smart phones, wind turbines and missiles -- at the plant in Malaysia's Pahang state. The rare earths are to be imported from Australia.

The Malaysian government has said it will closely monitor the company's handling of radioactive waste. Lynas has insisted the plant will be safe.

Fuziah said the plant should not be allowed to open as no detailed study had been done to assess its impact on the environment and residents.

"What if there is a leakage? What if there is migration of the radioactive material into the water and soil?" Fuziah told AFP.

"There should be a real detailed study."

Analysts say the plant, able to process an initial 11,000 tonnes of rare earths per year, will help break a Chinese stranglehold on the materials that has crimped supply and sent prices soaring in recent years.

China currently meets about 95 percent of world demand.

Lynas hopes to begin production in the middle of the year.

But activists have vowed to step up their protests ahead of general elections widely expected to be called this year. A rally in the seaside town of Kuantan near the plant is scheduled for later this month.

Opponents point to a similar rare earths plant in Malaysia's northern Perak state forced to shut down in 1992 over protests from residents who blamed it for birth defects in nearby populations.