abuja/dakar cameroonian troop month cross nigeria pursuit rebel without seek authorization nigeria cause falling-out governments behind scenes source familiar matter tell reuters least one incursion confirm nigerian government official two nigerian military officer two foreign diplomats speak condition anonymity nigerian security force deploy border stop cross say military source cameroonian nigerian governments say separate statements incursions relations two countries good cameroon say cameroonian military officials pro-government media accuse nigeria shelter anglophone insurgents past year base dense equatorial forest straddle border two countries fight independent state call ambazonia least 7,000 people flee refugees anglophone cameroon nigeria follow crackdown order year president paul biya quell insurgency represent grave challenge yet 35-year rule french official language cameroon two regions speak english border nigeria also anglophone cameroonian troop nigeria say foreign diplomat zero warn zero authorization troop cross nigeria least twice month diplomat nigerian military official tell reuters incidents cause anger side could sour diplomatic relations cameroon increase pressure anglophone regions accord diplomat nigerian government official tensions high could escalate government official say cameroon government spokesman issa tchiroma bakary deny troop cross border illegally relations two countries cohesive come fight terrorism cameroon nigeria wavelength nigeria foreign minister speak reuters cabinet meet abuja also deny incursions nigerian government investigate discover true say geoffrey onyeama nigeria foreign minister nigerian government official diplomat say cameroon threaten suspend senior nigerian embassy officials yaounde lodge complaints tchiroma onyeama deny governments africa often play diplomatic dispute present show harmony even bitter row monday rebel kill four gendarmes cameroon government say late raid police military position country southwest region nigeria decades west africa powerhouse militaries two countries cooperate extensively confront threat pose islamist militant group boko haram group stag attack nigeria years recently also conduct deadly assault cameroon cameroon repeatedly press nigeria allow right hot pursuit boko haram militants issue leave countries loggerheads cameroon military cross border month pursuit separatist insurgents nigeria send security force deter future attempt say one military source war keep peace protect territorial integrity ask leave everything bring control source say many refugees cross nigeria many still cross cameroon authorities appear concern situation may escalate keep come nigeria two cameroonian military officials speak condition anonymity tell reuters separatists set base launch attack nigeria one attack dec. 14 involve two group least 100 separatists one officials say explain guy come attack us leave without trouble across border drive back separatists withdraw toward nigeria official say julius ayuk tabe nigeria-based chairman ambazonian govern council political wing arm resistance say aware separatist military base nigeria cameroon linguistic divide hark back end world war one german colony kamerun carve ally french british victors english-speaking regions join french-speaking republic cameroon year independence 1960. french speakers dominate country politics since exclusive cameroonian troop enter nigeria without seek authorization source nigeria say