Four Salafists were killed and at least six others injured on Wednesday in an armed attack by Shiite Houthi rebels in Yemen\'s southern province of Saada, tribal leaders and witnesses said. \"Four Sunni men were killed in shelling by armed Houthis in al- Toloul and Bouraikah mountains near the town of Dammaj,\" tribal leader Abdul Kadir al-Odainy told Xinhua by phone.