He was with a group which also included AFP and Al Jazeera journalists.
AFP photographer Christina Assi and video journalist Dylan Collins were also injured and were undergoing medical treatment.
There have been unsubstantiated reports that it was Israeli artillery fire.
Issam AbdallahIssam Abdallah Instagram
Reuters did not comment on these reports and said it was still investigating the matter.
Abdallah posted video of an explosion in southern Lebanon about two hours before his death was confirmed.
Our thoughts are with his family at this terrible time, read its statement.
Israel declared war on Hamas and launched strikes onGaza.
Nine Palestinian journalists were confirmed dead and one Israeli journalist was killed, according to the group.
