SITTWE - Armed troops patrolled the northwest Myanmar city of Sittwe on Friday after days of sectarian violence that has stoked nationalist fervor and displaced 30,000 people, with many feared dead. Heavy rain kept many residents indoors in the Rakhine state capital and police and aid groups struggled to get food to thousands of ethnic Rakhine Buddhists and Muslim Rohingyas displaced by communal rioting and arson that have presented a big test to Myanmar's 15-month-old quasi-civilian government. United Nations officials told Reuters three of its staff, two from its UNHCR refugee agency and one from the World Food Programme (WFP), all Myanmar nationals, had been detained by police in the Rohingya-dominated town of Buthidaung for unknown reasons. The WFP had provided hundreds of sacks of rice to some areas, said Aye Win, spokesman for its operations in Myanmar. "We will try to get to other camps as soon as we can, when it is safe and secure. We are doing as much as we can. We will go in but security is paramount," he added. More than 20 houses were burned down late on Thursday in a village near Sittwe, residents said, adding to the 2,500 torched in the past week. But there were no reports of further deaths. The violence, which the government said had killed 29 people and displaced 30,000 as of Thursday, is a major setback for a rapidly reforming Myanmar that has seen a year of dramatic political change after 49 years of oppressive military rule. The new government has made peace and unity among Myanmar's many ethnic groups its mantra and has struck ceasefire deals with minority Karen, Shan, Mon and Chin rebels, among others, after decades of hostilities. The Muslim community's Friday prayers were cancelled in Sittwe and surrounding villages to avoid a repeat of riots that erupted in the town of Maungdaw a week ago and spread to other parts of Rakhine state. "Officials do not want large gatherings and want to avoid more violence. They (Muslims) will be able to pray at home," Shwe Maung, a Muslim member of parliament for the ruling Union Solidarity and Development Party, told Reuters.