An Islamic jihadist group is pushing a campaign to further spread Islam in Spain with the ultimate objective of reconquering the European country by urging migrant Muslim men to marry local Christian women.

The group has posted hundreds of posters in the Muslim migrant-dominated El Raval neighbourhood of Barcelona inviting members of the Muslim community there to an "information meeting" on March 14, Breitbart reported.

"It is permissible and encouraged that the Muslim man marries honest and chaste women who belong to the People of the Book [Christians]. Even though they have distorted and altered the tradition, they are still suitable for marriage," the English translation of the poster's Spanish text reads.

"Brother, enter a partnership with a Spaniard, teach her that Islam is the true religion. Islamic law dictates that the fruits of this alliance will follow Islam, which will further strengthen our community," it says.

Muslim jihadist groups have long been saying that followers of Islam have a "right of return" to Spain, which was once called Al-Andalus by its Muslim conquerors. Muslims known as Moors ruled Spain, Portugal and southern France from 711 to 1492, when the last Muslim bastion of Granada fell to the Christian Castillian Army.

One jihadist group called Restore Sanctity in Al-Andalus is using social media to wage a campaign for Muslims to reclaim Spain. In a Facebook post, the group recommends El Raval as one of "suitable places" for Muslims migrating to Spain to live. It says this is the "first stage" of recreating Al-Andalus.

"We exercise our right of return, Al-Andalus is our home," it says.

The social media campaign started in 2014, according to the Gatestone Institute.

The campaign involves posting images of famous Spanish landmarks and monuments emblazoned with Arabic slogans such as, "We are all the Islamic State" and "Long Live the Islamic State."

The Islamic State once came out with a video where they vowed to liberate Al-Andalus from non-Muslims and make it part of their new Islamic caliphate.

As noted by the Gatestone Institute, radical Muslims—and even many moderate Muslims—believe that all the lands Muslims lost during the Christian reconquest of Spain and the surrounding regions still belong to the Islamic realm. These Muslims also claim that Islamic law gives them the right to return and re-establish Islamic rule in Spain.