Hillary Clinton, the US secretary of state, has called on international oil companies to stop operating in Syria, saying that hitting the energy sector would punish the Assad regime as it continues to crack down on anti-government protesters. Her plea came amid reports of more shelling in the eastern Syrian city of Deir Ezzor and deaths in the central city of Homs. The US has been trying to drum up international support for sanctions against Syria's oil and gas sector, which provide as much as a third of the regime's revenues, but has so far failed to convince other countries to join the effort. US companies have negligible involvement in Syria, so unilateral sanctions would have little effect. "What we really need to do to put the pressure on Assad is to sanction the oil and gas industry," Mrs Clinton said in an interview with CBS. "We want to see Europe take more steps in that direction and we want to see China take steps with us. We want to see India." Earlier, Victoria Nuland, state department spokeswoman, said that Washington was "encouraging" energy companies trading with Syria to stop "so that the pinch will be felt and none of the revenue from this can go to fuelling this violence". Italy, the Netherlands, France and Germany all buy heavy crude oil from Syria, while European oil giants, including Royal Dutch Shell and Total, are heavily involved in exploration and production, as is Petro-Canada. Chinese and Indian companies are also working on the production side <b>...</b>