N'Djamena - Over 3 000 Nigerians have fled to Chad to escape attacks in northern Nigeria by Islamist extremist group Boko Haram, government officials said on Wednesday."Since mid-December we've witnessed a massive influx of Nigerian refugees in the Lake Chad region" bordering Nigeria, Chadian Prime Minister Kalzeube Pahimi Deubet told diplomats and other international officials in N'Djamena.Civilians fled their homes on the shores of Lake Chad in north-eastern Nigeria at the weekend after a series of Boko Haram raids in which they seized a military base and several villages."To date, we've recorded over 3 000 Nigerian refugees and 543 'returning' Chadians" fleeing "instability in certain neighbouring countries, particularly Nigeria due to Boko Haram," Deubet said."We fear this could lead us into an uncontrollable situation if we don't take measures in time."The problem is both humanitarian, and one of security. The humanitarian situation is worrying and requires international support, because disease has now broken out," he said, adding that Chad is deploying forces to ensure the safety of the refugees.Michel Waibo, representative of the African Development Bank, warned that "all partners are aware that Chad must not be overwhelmed in a way that would create problems and disorder in African in general, and central Africa in particular".Boko Haram, which has declared a "caliphate" in the zones it controls in northeast Nigeria, is also increasingly active on the borders of Niger and Cameroon.In a 5 January video, its leader, Abubakar Shekau, threatened Cameroonian President Paul Biya with the same kind of attacks with which it has taken control of much terrain in Nigeria.