Google Inc (GOOGL.O) is in early talks to buy Bangalore-based start-up InMobi, in a move that would strengthen its offering in the increasingly competitive mobile advertising space, a source with direct knowledge of the matter said. InMobi, which helps companies target phones and mobile devices in their advertising, was launched in 2007 and claims to have over 1 billion users across 200 countries. The source said Google had not yet detailed its terms and conditions for the deal. InMobi would likely be valued at around $1 billion, the source said.