Tunisia's women's ministry said Saturday it would come up with a plan to counter the growing number of women travelling to Syria to wage so-called "sex jihad" by comforting militants.

"The ministry intends to boost its cooperation with both government and non-government bodies on this issue to come up with appropriate ways to thwart the plans of those who encourage such practices," a ministry statement said.

"The ministry will work to introduce a plan of information, sensitivity and education targeting women and families everywhere to warn them of the seriousness of these practices," it said.

A crisis group has already been set up, it added.

Interior Minister Lotfi ben Jeddou told the National Constituent Assembly on Thursday that Tunisian women had gone to Syria where "they have sexual relations with 20, 30, 100" militants.

"After the sexual liaisons they have there in the name of 'jihad al-nikah' -- (sexual holy war, in Arabic) -- they come home pregnant," he told MPs.

Ben Jeddou did not elaborate on how many Tunisian women had returned to the country pregnant with the children of jihadist fighters.

On Saturday, the health ministry statement said it had noted "an increase in the number of young women leaving for so-called jihad al-nikah", although it did not give any figures.

Jihad al-nikah, permitting extramarital sexual relations with multiple partners, is considered by some hardline Sunni Muslim Salafists as a legitimate form of holy war.