The Algerian coastguard have reportedly shot dead two tourists holidaying in Morocco who strayed into Algerian waters on their jet skis.
They were among four French-Moroccan dual nationals who had set off by jet ski from the Moroccan resort of Saidia.
A third member of the group was arrested by the coastguard which patrol the two states’ closed border.
The shooting sparked anger in Morocco after a fisherman posted video of a lifeless body floating in the sea.
The border between Algeria and Morocco was closed in 1994, with Algiers severing ties two years ago. It accused Morocco of hostile acts – an allegation rejected by Rabat.
Mohamed Kissi was the only one of the group of four to make it back to Morocco, AFP news agency reports, quoting Moroccan media. He said the group had got lost and had run out of fuel.
“We got lost but we kept going until we found ourselves in Algeria,” said Mr Kissi, whose brother Bilal was killed.
“We knew we were in Algeria because a black Algerian dinghy came towards us” and those on board “fired at us”, he said.
“Thank God I wasn’t hit but they killed my brother and my friend,” he added.
“They arrested my other friend. Five bullets hit my brother and my friend. My other friend was hit by a bullet.”
He was eventually picked up by the Moroccan navy and brought back to Saidia, he added.
Abdelali Merchouer has been named as the second man killed.
The man arrested by the Algerian coastguard, named as Smail Snabe, reportedly appeared before a prosecutor on Wednesday but no details were given.
A Moroccan government spokesman declined to comment on the shooting, telling AFP it was “a matter for the judiciary”.
There was no immediate comment from Algeria.
The two nations have a long history of tensions, as they continue to dispute Western Sahara.
They share a border nearly 2,000km (1,242 miles) long which has been a source of tension since independence from French colonial rule.
It was closed in 1994 for security reasons after Islamist militants bombed a hotel in the historic Moroccan city of Marrakesh.