The UN Security Council approved a resolution Monday demanding Syria co-operate with a UN investigation into the assassination of Lebanon's former prime minister, threatening further action against Damascus if it continues to stonewall. Syrian border police keep watch. INDEPTH: Syria The resolution was unanimously approved by the 15-member council after the threat of economic sanctions was dropped from a previous resolution, co-sponsored by the U.S., France and Britain. Russia and China had objected to the initial text which called for the threat of economic sanctions unless Syria co-operated with an investigation into the bombing that killed Rafik Hariri and 20...