Tanzania has asked Malawi to stop oil and gas exploration activities in Lake Malawi until a border dispute between the two countries involving the lake is resolved, a Tanzanian official said on Monday.Last October, Malawi said it had awarded oil exploration licences to UK-based Surestream Petroleum to search for oil in Lake Malawi, which is also known as Lake Nyasa in Tanzania."Malawi claims that the whole lake belongs to the country according to colonial boundaries ... But our stated position is that half of the lake belongs to Tanzania," said Assah Mwambene, a spokesman for Tanzania's foreign affairs ministry.Lilongwe awarded Surestream Petroleum licences for blocks 2 and 3 in the disputed lake, with a combined area of 20,000 square kilometres.Tanzanian officials said the 50-year-old territorial dispute between the two countries could escalate if significant oil and gas discoveries are made in the lake.Mwambene said Tanzanian Foreign Affairs Minister Bernard Membe told his Malawi counterpart, Mganda Chiume, that ongoing oil exploration at the lake could jeopardise talks between the countries over the dispute.The two ministers met in Dar es Salaam at the weekend to discuss the territorial dispute, Mwabene said."Some planes have been spotted flying over Tanzania's side of the lake conducting the oil exploration activities ... there is still room for negotiations over the correct border between Tanzania and Malawi," he said.Tanzania, which made huge natural gas discoveries off its Indian Ocean coast, said last month it had nearly tripled its estimate of recoverable natural gas reserves to as much as 28.74 trillion cubic feet.