Police in Saudi Arabia arrest six men on terror charges Police have arrested six men on terror charges after an attack killed five people in the restive eastern province of Saudi Arabia, prompting fears of a rise in sectarian violence as the Gulf kingdom grapples with the threat of domestic Islamist extremism. Nine people were also wounded in the machine gun attack late on Monday in al-Dalwah, a town in al-Ahsa governorate, a population centre for the Shia minority in the Sunni-ruled monarchy. The state news agency, quoting an interior ministry spokesman, said simultaneous operations in al-Ahsa, as well as the city of al-Khobar in the east and Shaqra, near Riyadh, the capital, had led to the arrest of six people "involved in the terrorist crime." Videos circulating on social media appeared to show the aftermath of the attack, which apparently took place as worshippers left a Shia religious building. Shia are this week celebrating Ashura, commemorating the death of the Prophet Mohammed's grandson in a battle that led to the 1,300-year-old schism between Shia and Sunni Islam. The 10-day religious festival often attracts inter-communal violence. The al-Dalwah attack comes as Saudi Arabia, a member of the US-led coalition against the Islamic State in Iraq and the Levant, known as Isis, braces itself for an overspill of radicalism via domestic Islamist extremists. In Iraq there has been an increase in attacks on Shia neighbourhoods as the government battles Isis forces across the country. Observers have expressed concerns that Isis sympathisers could also launch attacks against Shia Muslims or foreigners in Saudi Arabia, copying the brutal tactics of jihadi groups against those whom they regard as apostates. Thousands of Saudis have joined the ranks of jihadi fighters in Syria and Iraq, many encouraged by firebrand clerics who often stir up religious sentiment against non-Sunnis. While the government has cracked down on jihadi sympathisers, Islamist extremist groups share some aspects of the conservative strain of Wahhabi Islam propagated in the kingdom. Tensions have already been rising in the Shia-dominated towns of al-Ahsa and al-Qatif since a leading cleric was sentenced to death for sedition. Sheikh Nimr al-Nimr led protests in Qatif during the height of the Arab revolts of 2011. In neighbouring Bahrain, frequent protests persist led by the majority Shia against minority Sunni rule. Attempts to resolve the stand-off between the government and Shia activists have so far failed, raising the prospect of continued unrest. The Shia in Saudi Arabia claim economic and religious discrimination, saying they find it harder to secure state jobs and set up places of worship. The authorities deny the claims. Sunnis fear that the Shia harbour political loyalty to co-religionists in Iran, the Sunni Gulf states" regional rival.