Cox's Bazar - Bangladeshi authorities are taking steps to restrict the movement of Muslim Rohingya refugees living in crowded border camps after fleeing violence in Myanmar, whose military chief maintains that the chaos was the work of extremists seeking a stronghold in the country.Bangladesh has been overwhelmed with more than 400 000 Rohingya who fled their homes in the last three weeks amid a crisis the UN describes as ethnic cleansing. Prime Minister Sheikh Hasina, who lambasted Myanmar for "atrocities" during a visit to border camps last week, left Dhaka to address the annual UN gathering in New York.Refugee camps were already beyond capacity and new arrivals were staying in schools or huddling in makeshift settlements with no toilets along roadsides and in open fields. On Sunday, police were checking vehicles to prevent Rohingya from spreading to nearby towns in an attempt to control the situation."There is an instruction from the prime minister that we must treat Rohingya Muslims maintaining human rights," said AKM Iqbal Hossain, a police superintendent.Immunisation With the UN saying there are about 240 000 children among the refugees living in dire conditions, Bangladeshi authorities have kicked off a massive immunisation drive. Abdus Salam, the top government administrator in the Cox's Bazar district hospital, said that about 150 000 children would be immunised over seven days for measles, rubella and polio."There are a lot of weak and malnourished children among the new arrivals," Unicef's representative in Bangladesh, Edouard Beigbeder, said in an email. Eric P Schwartz, head of the US-based charity Refugees International and a former assistant secretary of state for population, refugees and migration, said he couldn't recall seeing so much misery and called for international pressure on Myanmar to stop the violence.