Palestinian armed groups have used a new type of bomb in their fight against Israel.
Two barrels with explosives that washed up on Israeli shores earlier this week - but were defused safely - are being called "floating bombs".
A number of Palestinian armed factions say their motive for the bombing attempt was to avenge an Israeli raid in the West Bank last month that killed three Fatah members.
Israel says it's taking the threat seriously.
Al Jazeera's Ayman Mohyeldin reports from Gaza.
Source: Al Jazeera