Algeria said Thursday it had summoned Morocco's ambassador after a video circulating on social media appeared to show a Moroccan diplomat calling Algeria an "enemy" country.
Relations between the North African countries have long been tense, particularly over the Western Sahara, a disputed former Spanish colony on Africa's Atlantic coast that is mostly under Morocco's control.
Algerian Foreign Minister Sabri Boukadoum summoned Rabat's ambassador on Wednesday over "comments by Morocco's consul general in Oran during an exchange with Moroccan citizens", his ministry said in a statement carried by the official APS agency.
In the widely shared video, a man presented as the consul of Morocco in Algeria's second city Oran is seen speaking to Moroccans complaining about being stranded there due to coronavirus travel restrictions.
The diplomat is seen trying to explain the difficulties involved in their repatriation, and is heard saying, "this country is your enemy, to tell you frankly".
Algeria has backed the Western Sahara's Polisario Front, which fought a war for independence from Morocco between 1975 and 1991, and demands a referendum on self-determination.
Morocco, which maintains that Western Sahara is an integral part of the kingdom, has offered autonomy but insists it will retain sovereignty.
United Nations-led negotiations are at a standstill.
The shared frontier between Algeria and Morocco has been closed since 1994, and Morocco has shut its other borders to stem the spread of the novel coronavirus.
The Algerian foreign ministry warned that a diplomat calling it an "enemy country" would constitute a serious violation, and urged Rabat to take "appropriate measures" to protect bilateral relations.
The incident came after Moroccan Foreign Minister Nasser Bourita said earlier this month that a "neighbouring country continues to fuel separatism".
The comments were cited by Moroccan news agency MAP, which added that they referred to Algeria.
Moroccan King Mohammed VI last year called for a "new page" on relations with its neighbour, after the election of Algerian President Abdelmadjid Tebboune in December.