Libya’s national oil company has warned shipowners of “unauthorised” attempts by rival factions to export crude, in further evidence of the power struggle between east and west over oil revenues. In a letter circulated among London traders and shipbrokers, the Tripoli-based National Oil Corporation (NOC) said it had become aware of several companies trying to charter ships to load illicit cargoes of Libyan oil at the Marsa el-Hariga export terminal. Oil purchase agreements had been signed between a handful of foreign companies and Libyan individuals claiming to act on the authority of the rival government based in the east, the NOC said. “Shipping market participants are advised that these contracts and the individuals who signed them have no legal standing,” said Ahmed Shawki, the NOC’s general marketing manager in a letter addressed to Katharina Stanzel, managing director of oil tanker association Intertanko.