The Islamic police in Nigeria's northern state of Kano arrested nine Muslims on Wednesday who were seen eating food during the first day of this year's Ramadan fast.

Kano has a majority Muslim population, where an Islamic legal system - Sharia - operates alongside secular law.

The Islamic police, known as the Hisbah, search cafes, restaurants and markets every year during Ramadan to ensure Muslims are adhering to the fasting hours. Some establishments stay open in areas of Kano where many Christians live.

For Muslims, eating is prohibited between sunrise and sunset. Fasting is one of the Five Pillars of Islam, which lay the basis for how Muslims are required to live their lives.

Hisbah's deputy commander general Mujahid Aminudeen told the BBC that the nine detained - seven males and two females - had feigned ignorance that Ramadan had begun.

"We have arrested them and they are with us where we are going to be teaching them the importance of fasting, how to pray, read the Quran and become better Muslims," he said.

It is not clear when the Hisbah plans to free them. In similar cases in the past, officers have got in touch with the families of those detained to make sure there is proper monitoring after their release so that they fast to the end of the month.

Just over two decades ago, Sharia was introduced to work alongside secular law in 12 of Nigeria's northern states that all have a majority Muslim population.

Ramadan is the ninth month of the Islamic calendar and has a special significance in Islam.

It is during this month that Muslims believe the first verses of the Quran - Islam's holy book - were revealed to the Prophet Muhammad.

Every year, Ramadan is expected to last between 29 or 30 days. In Nigeria, fasting started on Wednesday 18 February and it is predicted to end on either 21 or 22 March.