A Moroccan NGO on Monday called on Spain to look into allegations that it used poison gas in the so-called "Rif War" between the two countries almost one century ago.
Both Spanish and Moroccan historians have accused Spanish forces of having used chemical weapons during the conflict, which is also known as the War of Melilla.
The conflict, which lasted from 1920 to 1927, pitted Berber rebels led by Mohamed Ibn Abd al-Karim al-Khattabi against Spanish colonial forces in Morocco's Rif region.
In a Monday statement, the Center for Common Memory for Democracy and Peace, a Moroccan NGO, urged Spanish Foreign Minister Alfonso Dastis to follow up on earlier pledges to look into claims by Moroccan civil society institutions "regarding the use [by Spain] of chemical weapons in the Rif region during the colonial period".
The NGO went on to assert that "priority must be given to the issue of chemical weapons use and the tragedies they have caused — including the spread of cancerous diseases — in areas that were bombed [by Spanish colonial forces during the conflict]".
Read: Morocco receives 43,000 documents from France about Moroccan Jews
It added: "This issue, along with other outstanding legal issues between Spain and Morocco, must be resolved in line with human rights conventions and mechanisms for transitional justice."
The NGO went on to call for the establishment of a committee — composed of legal and human rights experts from both countries — to discuss means of addressing outstanding legal and ethical issues.
The Rif War was an armed conflict between Spain, still a colonial power at the time, and the Berber tribes of Morocco's Rif Mountain region.
The conflict ended with a Spanish victory and the dissolution of the self-styled Rif Republic.