An oil spill from the Trans-Israel pipeline in the Evrona nature reserve north of Eilat is causing what has been described as one of the worst ecological disasters in Israel's history.

The Eilat-Ashkelon Pipeline Company (EAPC) acknowledged on Monday that the spill was much larger than previously thought and about 5 million litres of crude had gushed out in the desert.

Emergency attempts are being made to pump the oil out before a winter downpour accelerates seepage into underground water reservoirs or towards Eilat Bay, where it could damage the Red Sea coral reef.

The spill happened last Wednesday during work to relocate part of the pipeline away from a new road to Eilat airport, which is under construction. By Monday, only about 40 per cent of the oil had been pumped out, along with 13,000 tons of polluted ground.

Ecologists say that it could take decades for Evrona, previously the best preserved saltland in the southern Negev desert, to recover from the damage.

The spill has put EAPC under an unaccustomed spotlight. The Trans-Israel pipeline was originally a joint Israeli-Iranian project to transport Iranian oil from Eilat port to Ashkelon on the Mediterranean coast, and from there onwards to Europe. The Islamic Revolution in 1979 ended that arrangement, but the pipeline has transported oil for other customers since then.

Energy supply is considered a strategic matter in Israel and is therefore subject to military censorship. Following last week's oil spill, politicians and environmentalists have called for end to the news blackout on EAPC's affairs.