The US's top military officer has warned Syria it could face armed intervention as international outrage grows over the massacre of women and children by tanks and artillery in Houla.

General Martin Dempsey, the chairman of the joint chiefs of staff, said that following the UN security council's condemnation of the slaughter – in which more than 100 people were killed, many of them children – there needed to be increased diplomatic pressure on Damascus. But he added that the US would be prepared to act militarily if it was "asked to do so".