Russia's Gazprom took further steps to strengthen its hold on natural gas supplies to Europe on Thursday, signing a joint venture with Libya and saying it was in preliminary talks on a multibillion dollar project to pipe Nigerian gas to Europe across the Sahara. News of the two projects came as Vladimir Putin, Russian president, became the first Russian leader since 1985 to visit Libya. According to the country's official news agency, Libyan leader Muammer Gaddafi said during talks with Mr Putin he supported the idea of forming an Opec-style group of gas-exporting countries.