Air China said Tuesday it is cutting back flights to Japan over safety worries after a vast earthquake and tsunami, while Taiwan's EVA Airways cancelled some flights to Tokyo and Sapporo.

Malaysia's main airport began screening passengers returning from Japan for radioactive contamination as the quake-hit nation fought a nuclear crisis at a power plant, and South Korea said it was considering a similar measure.

But Air China said its worries were over aftershocks rather than radiation, while other Asian airlines said they would keep flying to Japan as normal apart from tsunami-hit Sendai.

Several countries in the region sought to dampen public fears over the nuclear emergency, saying they did not think they needed to screen those leaving Japan for radiation, although the situation worsened Tuesday with two more blasts at the stricken atomic plant.

Radiation around the Fukushima No. 1 plant reached levels dangerous to human health, the prime minister's chief spokesman said. Higher than normal radioactivity was also detected in Tokyo but it was not thought to be harmful.

The Chinese flag carrier cancelled half of its six daily Beijing-Tokyo flights for Tuesday and Wednesday, and one of its three Shanghai-Tokyo flights for each of the two days.

"We have cancelled some of the flights from China for safety reasons. But most flights remain normal," Air China spokeswoman Zhu Mei told AFP.

"The cancelled fights were those scheduled to stay one night at Japan airports. The planes could face danger in the event of aftershocks."

The airline's flights to Sendai were on hold after the airport there was flattened by the tsunami that swept the country's northeast after Friday's 9.0-magnitude quake.

But Zhu said so far she knew of no new disruptions over radiation fears.

"We have not received a notice (on the radiation issue)," she said. Air China was not screening any incoming passengers for radiation.

Taiwan's EVA Airways cancelled 14 flights scheduled to leave for Tokyo before the end of March and another five to Sapporo, as well as calling off all flights to Sendai until June 30, a spokesman for the firm said.

He blamed cancellations by tourists after the devastating twin natural disasters. The island has not so far carried out radioactivity screening.

But the company that runs Malaysia's airports said it was checking passengers for radiation as they emerged off direct flights from Japan.

"The screening started on Monday morning, involving three airlines which fly directly to Tokyo -- Japan Airlines, Malaysia Airlines and AirAsia X," a spokeswoman for Malaysia Airports Holdings Berhad told AFP.

Officials from national carrier Malaysia Airlines and long-haul budget carrier AirAsia X said their flights were operating on schedule, however.

South Korean flights to Japan were operating as normal -- except to Sendai -- a spokesman for Incheon airport said, while Australian airlines Qantas and Jetstar said their flights were going ahead.

Indonesian and Hong Kong authorities and Singapore Airlines said their flight schedules would proceed, with Hong Kong saying passengers from Japan concerned about radiation exposure could visit a public hospital for a test.

Countries including Australia and Thailand have already urged their nationals not to go near the stricken plant and to reconsider travel to other areas affected by Friday's 9.0-magnitude quake and the subsequent tsunami.

Head of the International Atomic Energy Agency Yukiya Amano said Tuesday it was "very unlikely" Japan's problems could grow to resemble the nuclear crisis at Chernobyl in Ukraine, which caused widespread contamination in 1986.

burs-je/slb