A Buddhist monk has been arrested in Myanmar after a grenade, ammunition and more than four million methamphetamine pills were found in his car and in his monastery.

Police officer Maung Maung Yin said the monk was stopped Sunday (local time) as he drove in northern Rakhine state, which borders Bangladesh.

Authorities had been tipped off that the monk was carrying an illegal haul.

An anti-drug task force then found 400,000 pills in the monk's car, Maung Maung Yin said.

A subsequent search of his monastery turned up 4.2 million pills along with a grenade and ammunition.

A statement from the office of Myanmar's leader, State Counsellor Aung San Suu Kyi, said that one million kyats ($959) in cash was also found in the vehicle.

'Not a normal case'

Myanmar is a major producer of methamphetamine, usually smuggled from the north-east to neighbouring countries.

It is also the world's second biggest producer of opium, from which heroin is derived.

"This is not a normal case, and when we were informed that the monk was arrested, we were all shocked," said Kyaw Mya Win, a township police officer.

Asked about the case, the director general of the Religious Affairs Ministry, Soe Min Tun, acknowledged some surprise.

"It is not a very common case, but not impossible to happen. What will happen to the monk is that he will have to give up his monkhood right away and face trial as an ordinary person," he said.

Police said they were still questioning the monk on Tuesday.

Last year, Myanmar officials seized 21 million methamphetamine pills, with a street value around $46.6 million, near the border with China in the biggest such seizure in recent memory.

AP