London - Britain's Foreign Office warned against all travel to South Sudan on Saturday after two days of fighting between government forces and former rebels.The Foreign Office said that its decision came as the security situation in the capital Juba had "deteriorated" since Thursday."British Embassy staff have been on lock-down and we are reducing to only essential staff in the country," it said in a statement on its website."If you have no pressing need to remain, you should consider leaving (by commercial means), if it is safe to do so."It added: "The Foreign and Commonwealth Office advise against all travel to South Sudan."More than 150 soldiers died in fighting between the army and former rebels in Juba on Friday, according to a spokesperson for rebel leader turned Vice President Riek Machar.The fighting began when President Salva Kiir and rebel leader turned vice president Machar met at the presidential palace and initially involved each man's bodyguards.On Saturday morning tension remained high in the city, with a heavy security presence and few civilians on the streets of Juba.Saturday is the fifth anniversary of the country's independence.