Algeria has suspended a two-decade-old friendship treaty with Spain.

Relations between Algeria and Spain have deteriorated since March, when Madrid openly backed Morocco's plan to grant autonomy to Western Sahara, which Rabat annexed in 1975 when Spanish forces withdrew from the region.

Algiers supports the region's Polisario independence movement, which has led to steadily worsening ties between the neighboring North African countries.

Under the friendship treaty signed in 2002, Algeria and Spain agreed to cooperate on controlling the flow of migration and fight against human trafficking.

Spain's foreign ministry issued a statement saying it regretted Algeria's decision but remained committed to upholding the principle of the treaty.

The growing tensions between Algeria and Spain could also further complicate Algeria's role as a key supplier of natural gas to Spain. Algiers stopped pumping gas to Spain through a pipeline that passes through Morocco last year.

Some information for this report came from The Associated Press, Reuters and Agence France-Presse.