UN Assistant Secretary General for Political Affairs Oscar Fernandez-Taranco has called on Israel to end its "unacceptable" blockade of the Gaza Strip.

Fernandez-Taranco, who was speaking at an emergency meeting of the UN Security Council, said that Israel's Monday attack on peace activists on a flotilla of ships off the coast of Gaza would not have happened without the blockade.

He was speaking in proxy for UN Secretary General Ban Ki-moon, DPA reported.

The UN official also called for a thorough investigation into the Israeli military assault on the ships.

Fernandez-Taranco stated that the incident happened when all efforts should be focusing on confidence-building and on promoting talks between Israelis and Palestinians.

The UN Security Council started an emergency meeting on Monday after Turkey called for a meeting on the Israeli attack on the Freedom Flotilla.

The Israeli navy attacked the Freedom Flotilla, which was carrying humanitarian assistance to Gaza, in international waters in the Mediterranean Sea early on Monday, killing at least 20 people on board the six ships, mostly Turkish nationals.

About 50 others were injured, according to Palestinian sources.

UN tells Israel to end siege of Gaza