Female Islamic clerics in Indonesia declared a series of fatwas Thursday, including one to tackle child marriage, a rare example of women taking a leading religious role in the Muslim-majority country.

The fatwas were issued at the end of a three-day congress of female clerics in the country with the world's biggest Muslim population.

The meeting in Cirebon on Java island, billed as the world's first major gathering of female Muslim clerics, attracted hundreds of participants. Most were Indonesian but there were also clerics from Pakistan, India and Saudi Arabia.

They issued a series of fatwas at the end of the gathering, the most eye-catching of which was aimed at tackling child marriage. It urged the government to raise the minimum legal age for women to marry to 18 from the current age of 16.

The United Nations childrens' agency UNICEF defines child marriage as a formal marriage or informal union before age 18, and says women are most affected.

The problem is widespread in Indonesia, with one in four women marrying before 18, according to the agency.

Religious Affairs Minister Lukman Hakim Saifuddin, who attended the meeting, suggested authorities would examine the proposal: “I will take this recommendation to the government.”

He also praised the gathering: “This congress succeeded in fighting for justice in the relationship between men and women.”

Among the other fatwas issued was one against women being sexually abused; and one against environmental destruction, in a country that struggles every year with huge fires that are started illegally and devastate vast swathes of rainforest.

While the Ulema Council has issued rulings on environmental protection in the past, it tends to focus on religious topics such as edicts against blasphemy. It has rarely dealt with any issues affecting women.

About 90 per cent of Indonesia's population of 255 million people are Muslim.