DAJABON, Dominican Republic - (AP) -- Suspicion and tension are rife in the desolate hills along this sparsely guarded border, where armed Haitian rebels have returned from the Dominican Republic to join a growing revolt.

Haiti's government on Wednesday sought an explanation from Dominican authorities as old hostilities between the neighbors on the island of Hispaniola flared anew.

''We are asking ourselves how [armed rebels] could cross the border without the complicity of the Dominican army?'' Haitian government spokesman Mario Dupuy said in Port-au-Prince.

A former police chief accused of planning a 2001 coup attempt and an ex-leader of a paramilitary group reportedly crossed the border, according to witnesses who saw them with some 20 armed commandos in the rebel-held city of Gonaives.

The Dominican army said it had no knowledge of rebels crossing with guns, and residents in the border town of Dajabón said they hadn't seen any armed convoy.

Patrols are rare along much of the 225-mile border, which runs through hills and along the Río Masacre, a river sometimes shallow enough to walk across. Bribes are common at a riverside fence in Dajabón, where Haitian workers slip soldiers less than $1 each to cross.

Dominicans often complain about illegal Haitian immigrants. More than one million Haitians, mostly laborers, are estimated to live in this country.