Italy's Eni group and Kazakhstan's London-listed KazMunaiGas last night signed a preliminary agreement that could result in up to $50bn of investments in the central Asian state's upstream and downstream oil and gas sectors.

Separately Paolo Scaroni, Eni's chief executive, confirmed he had recently visited Turkmenistan where Eni has been labouring under a two-year visa ban for its employees following its purchase of Burren Energy of the UK, which operates an onshore Turkmen oil field.