Israeli leaders who ordered the attacks on a humanitarian aid convoy en route to Gaza should be brought to justice, a United Nations expert says.

"It is essential that those Israelis responsible for this lawless and murderous behavior, including political leaders who issued the orders, be held criminally accountable for their wrongful acts," Richard Falk, the UN Special Rapporteur on the situation of human rights in the Gaza Strip, said in a statement, AFP reported.

He made the remarks on Monday after the Israeli navy assaulted the Freedom Flotilla, which was carrying hundreds of activists and journalists and thousands of tons of supplies.

The raid left at least 20 people dead and 50 others injured, Palestinian sources told Press TV correspondent.

"Israel is guilty of shocking behavior by using deadly weapons against unarmed civilians on ships that were situated in the high seas where freedom of navigation exists, according to the law of the seas," said Falk.

Meanwhile, Amnesty International called for an "immediate, credible and independent investigation" into the Israeli raid, saying that Tel Aviv used excessive force.

"Israeli forces appear clearly to have used excessive force," said Malcolm Smart, the rights organization’s director for the Middle East and North Africa.

(Press TV)