The spill has polluted about 200 kilometres (124 miles) of the Lebanese and Syrian coasts, the EU said.

"Up to now, a total amount of recovered oil is close to about 100 tonnes in Jbeil where the European team and Lebanese civil defence worked together," a European Union (EU) statement said.

Lebanese environmental group Green Line has described the spill as the biggest environmental disaster in the Mediterranean basin, but officials said the scale of the threat is not yet known.

Senior officials from the United Nations, the European Union and regional states meeting in the Greek port city of Piraeus on Thursday unveiled a plan to clean up oil-clogged parts of the Lebanese coastline in an operation expected to cost at least 50 million euros (64 million dollars).

The plan, supervised by the United Nations Environment Programme (UNEP) and the International Maritime Organisation (IMO), prescribes immediate surveys by helicopter and a joint effort to clean up to 30 coastal sites in Lebanon.

UNEP executive director Achim Steiner said in Piraeus it was a matter of "utter urgency" to establish the size of the oil spill and to coordinate equipment, experts and financial support from donors.

In the meantime, the European team from Denmark and Norway, in cooperation with Lebanon's environment ministry, is identifying further areas where expert assistance is required and the team will attempt to start another clean-up operation in a Beirut port, the EU said.

"The targeted sites were designed by Lebanon and the priority was to de-pollute first harbours and beaches in order to restore economic activities," the EU statement said.

Officials warn that if all the oil from the damaged plant were to seep into the sea, the environmental fallout could rival the 1989 Exxon Valdez spill that devastated Alaska's Prince William Sound.

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