A town in Indonesia is banning women from straddling motorcycles, saying it is improper and against Islam.

Women in the town of Lhokseumawe will be told from Monday they cannot straddle a motorcycle or scooter, especially when sitting behind a man, and instead must ride side-saddle.

The mayor of the town, which is under strict Islamic sharia law, says the regulation is to protect women's morals.

"[It] is to maintain women's dignity and good image," said Suaidi Yahya.

But the move has drawn criticism from the country's biggest Islamic body, the Ulema Council, which say the Koran does not mention how to ride motorcycles.