Algerian President Abdelaziz Bouteflika warned Thursday of the risk of "chaos", on the eve of major planned protests against his bid for a fifth term in office.
The 82-year-old leader, who has been in Switzerland since late February for medical reasons, said in a message released by the official APS news agency that trouble-makers may try to infiltrate the rallies to provoke turmoil.
"Many of our fellow citizens" have demonstrated across the North African country "to peacefully express their views," he was quoted as saying.
"However, we must call for vigilance and caution in case this peaceful expression is infiltrated by some insidious party... which could cause chaos."
He made no mention of demonstrators' demands that he back down from his bid to seek re-election in April 18 polls, which has sparked waves of protest.
But echoing other senior Algerian officials, he warned of a return to the "national tragedy" of Algeria's decade-long civil war and of the "crises and tragedies caused by terrorism" in neighbouring countries.
Algeria has largely avoided the conflicts unleashed by the Arab Spring uprisings that brought down rulers in neighbouring Tunisia and Libya.
But discontent, particularly among the country's youth, turned to anger in February as the veteran leader announced another bid for power.
In office for two decades, Bouteflika uses a wheelchair and has rarely been seen in public since suffering a stroke in 2013.
Despite a ban dating back to 2001, demonstrations have been staged almost daily in the capital Algiers since a massive rally on February 22.