The Islamic police in Nigeria's northern state of Kano arrested 11 Muslims on Tuesday who were seen eating food during the Ramadan fast.

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

The Islamic police, widely known as Hisbah, carry out searches of eateries and markets every year during Ramadan.

The 10 men and one woman were released after swearing an oath that they would not purposely miss a fast again.

"We got 11 persons on Tuesday including a lady selling groundnuts who was seen eating from her wares and some persons alerted us," Hisbah spokesman Lawal Fagge told the BBC.

"The other 10 were men and were arrested across the city especially close to markets where a lot of activities happen."

He added that the search operations would continue but said that non-Muslims were exempt.

"We don't arrest non-Muslims because this doesn't concern them and the only time they could be guilty of a crime is when we find out they cook food to sell to Muslims that are supposed to be fasting."

Regarding those who were arrested he said that they were freed after promising to start fasting from now on and "for some of them we had to see their relatives or guardians in order to have family monitor them".

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. It 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.

Fasting is one of the Five Pillars of Islam, which lay the basis for how Muslims are required to live their lives. The fast is observed during daylight hours.

This year, Ramadan is expected to last 30 days, with fasting starting on Monday 11 March and predicted to end on Tuesday 9 April.