South Sudan has expelled the head of Chinese-Malaysian oil consortium Petrodar, the main oil firm operating in the new African nation, a top southern official said on Tuesday, escalating a row between Juba and Chinese oil firms.South Sudan has repeatedly attacked Chinese oil firms and launched an investigation into whether they helped Khartoum seize southern oil being exported from the landlocked country through Sudan. Juba has shut down its oil output of 350,000 barrels per day to end the seizures, which were sparked off by a dispute over transit fees."The (oil) minister has just expelled the president of Petrodar,” said Pagan Amum, South Sudan’s top negotiator for talks with Sudan over oil payments."I think one of the reasons is lack of cooperation by the President of Petrodar (with the government) and we have dismissed him and expelled him and we are asking the partners to appoint a new president,” he told Reuters during a visit to the Palouge oil field.Amum said relations with China were good but there were difficulties with some oil companies.Petrodar, which pumped 230,000 bpd and exported the southern oil through a Sudan pipeline until the shutdown, categorically rejected the accusations on Sunday and said it had followed only southern instructions .South Sudan’s attack on Chinese interests is puzzling Western diplomats because China is the biggest buyer of its oil.Petrodar is a consortium of mainly Chinese state firms Sinopec, Chinese National Petroleum Corp and Malaysia’s Petronas . It runs oil fields in South Sudan’s Upper Nile state, to which Palouge belongs, and also an export pipeline through Sudan. Many South Sudanese feel bitter about China because of its support for Khartoum during decades of civil war between the Muslim north and mainly Christian South that killed two million people. The conflict ended only in 2005 with a peace agreement that paved the way for southern independence.