ROME, July 21 (Reuters) - Italian authorities have seized a record 5.3 tonne cocaine haul being transferred between ships off the southern coast of Sicily, police said on Friday.

The consignment had an estimated value of 850 million euros ($946 million) and five people have been arrested, the Guardia di Finanza said in a statement.

Police had been tracking a ship that sailed from South America and swooped in the early hours of Wednesday, when a surveillance aircraft spotted packages being thrown from its deck into the waters of the Strait of Sicily to be collected by a waiting fishing trawler.