Algerian authorities have detained over 200 Moroccans at Algiers airport and summoned the Moroccan envoy to explain an "unusual" increase in the number of Moroccans apparently trying to cross into Libya, airport and government officials said on Sunday.
The foreign ministry and sources at the airport did not confirm why the Moroccans had been held, but diplomatic relations between Algeria and Morocco are often strained over their regional influence and cooperation.
Libya in particular has become a regional concern since Islamic State (ISIS) group militants gained ground there and called for foreign recruits, especially from North Africa. Tunisia, sandwiched between Algeria and Libya, is building a security wall along its boundary with Libya in an attempt to halt the flow of militant recruits crossing over.
"The question about the massive and unusual flow of Moroccans from Casablanca heading for Libya through Algeria in the last weeks was the reason for discussions with the ambassador," Algeria's foreign ministry said in a statement published on APS state news agency.
The current "particularly delicate" security situation required more vigilance and cooperation, the statement said without giving details.
The ministry did not mention the detentions. But a security source at Algiers airport said 270 Moroccans had been arrested on Saturday night. The source said the Moroccans were considered suspect because they did not have legal residence in Libya, though it was unclear if they had ties to militant groups.
Moroccan officials were not immediately available to comment on the detentions.
Algeria has become a pivotal partner in the Western fight against Islamist militancy in north and west Africa after its own 1990s war with armed Islamists that killed more than 200,000 people. Morocco has also helped French and European intelligence agencies after the Islamist attacks on Paris last year.
More than 3,000 Tunisians and hundreds of Moroccans have left to fight for Islamic State and other groups in Syria and Iraq. But experts say Libya has become an increasing magnet for North Africa Militants, partly because of the country's porous border controls and internal lawlessness.
ISIS group in Libya has steadily increased its presence, taking over Sirte, attacking oil installations and carrying out suicide attacks as the country has slipped into chaos with two rival factions and their armed groups fighting for control.