The UN refugee agency says Syrian survivors of the latest shipwreck involving migrants in the Mediterranean claim Libya's coast guard fired on their boat.
The UNHCR has asked Libya for an explanation.
Libyan Prime Minister Ali Zidan denied the allegations in a press conference on Sunday.
UNHCR spokeswoman Melissa Fleming said on Monday from Geneva survivors said their boat was fired on a couple of hours after leaving Zwara, Libya.
She says survivors told the agency the shooting damaged the ship's hull, possibly contributing to the sinking, and injured four people.
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The vessel sank 105 kilometres south of the Italian island of Lampedusa in Malta's search-and-rescue area.
Authorities say 34 people died. More than 200 people were rescued.
