Authorities were forced to issue advisories discrediting the reports, which circulated via mobile phone messages and social networking sites, while the justice secretary warned those behind the fake alerts could be prosecuted.

"There is no scientific and technical basis that a radioactive plume or nuclear fallout from Fukushima Daiichi Nuclear Power Plants will hit the Philippines," the Philippine Nuclear Research Institute said on Tuesday.

The hoax news alerts started spreading via text messages on the

Philippines' hyperactive mobile phone networks on Monday, as radiation leaked from Japan's quake and tsunami damaged Fukushima power plant.

One purportedly issued by a popular global television news network warned people to stay indoors, close doors and windows, and swab their necks with antiseptic to protect their thyroid glands.

"Radiation may hit phil starting at 4pm today. Pls send to ur loved ones," it said.

Some schools in the northern Philippines, about 2,800 kilometres (1,700 miles) away from the stricken power plant, sent their pupils home in the early afternoon on Monday.

The schools were apparently unaware that the news was a hoax, Cielito

Aglipay, an upset high school student's mother from the northern town of Batac, told AFP.

"The principal sent them home at 3pm. It was a false alarm," Aglipay said by phone.

Justice Minister Leila de Lima ordered the National Bureau of Investigation (NBI) to trace the source of the hoax SMS messages, saying they were liable for crimes against public order.

"There is a standing directive to the NBI to arrest those making prank calls or those making false alarms," de Lima told reporters on Tuesday.

"These are difficult and scary times, with these disasters happening, and we don't want to exacerbate the situation with those unfounded news."