The death toll from a tsunami which pummelled remote Indonesian islands soared to 311 today as questions mounted over whether an elaborate warning system had failed. President Susilo Bambang Yudhoyono was heading to the disaster zone, where fears were growing for hundreds still missing after huge waves triggered by a powerful earthquake on Monday hit the Mentawais off the west coast of Sumatra. Hundreds of kilometers away, a mass funeral is being held today for those killed when the nation's most active volcano erupted, the second natural disaster to strike Indonesia in as many days. West Sumatra disaster management official Agus Prayitno said that three hundred and eleven people were killed and 379 are still missing.