At least 18 people have been killed in a suspected suicide bomb attack at a Muslim shrine in the Pakistani capital, Islamabad.The Bari Imam shrine was said to have been packed with thousands of both Sunni and Shi’ite muslims taking part in a religious festival. Police said the initial signs were that it was a suicide bombing but did not speculate on the motive. The blast occurred in an area close to Pakistan’s main government buildings and the diplomatic quarter in Islamabad. Pakistan has seen an increase in violence between Sunni and and Shi’ite Muslims in recent years. The Bari Imam shrine is dedicated to a 17th century Sufi teacher who is Islamabad’s patron saint. But many conservative Muslims oppose popular Sufi practices including saint worship.