Israel said today the drowning of hundreds of Africans off Libya's coast was tragic but validated its own policy of having buffered its land barriers with Africa to keep migrants away.

Yisrael Katz, transport minister in Prime Minister Benjamin Netanyahu's outgoing cabinet, called the deaths in the Mediterranean a "tragedy that shocks all humanity" which also showcases Europe's difficulties in handling the migrant flow.

"Look at how correct the (Israeli) government's policy was to build a fence along the border with Egypt to block the way to labour migrants from Africa from reaching Israel," Katz, added in a post written on his Facebook page.

Israel reinforced a border fence with Egypt, its land bridge with Africa, in 2012, largely curtailing a flow of migrants that had been stealing into its midst for much of the past decade.

Since 2013 it has jailed hundreds of more than 40,000 African migrants, many of them having fled from troubled Eritrea and Sudan. Human rights groups charge this policy coerces many people eligible for refugee protection to seek repatriation at personal risk.

In addition to those held in a desert detention centre, thousands have received temporary visas and live in crowded impovershed parts of Israel and its business hub of Tel Aviv.

Israeli law grants automatic citizenship to Jews. The authorities have denied most Africans residency, shunning them as "infiltrators" seeking jobs rather than refuge.