A banned separatist civic organisation in Angola says some of its members were detained ahead of a visit by the president to the Cabinda region.
Cabindans say they are culturally and historically distinct
Jose Eduardo dos Santos' visit comes a year after a peace deal with most separatists in the oil-rich enclave.
Under the agreement, the region was awarded special status ending a 30-year conflict for independence.
But Mpalabanda, whose members are being held, told the BBC the conflict was ongoing and called for more talks.
"They [the government] try to convince all people that the established agreement was accepted by all parties, but it's not true, it's false," Mpalabanda President Agostinho Chicaia told the BBC's Focus on Africa programme.
He said three of their members had been detained without charge on Thursday. One has subsequently been released.
"For Cabindan people the president is not welcome because we don't have peace in Cabinda, we have a lot of problems and our priority is dialogue," Mr Chicaia said.
The province does not share a border with the rest of Angola - it is sandwiched between the Republic of Congo and the Democratic Republic of Congo on Africa's west coast.
The president is in Cabinda to open an airport and a supermarket.
Walter dos Santos from the BBC's Portuguese service says the visit is important politically as the president seldom leaves the capital, Luanda.
He says a faction of the Front for the Liberation of the Cabinda Enclave (Flec) that did not support the peace accord is still active in the bush.
But in the last year between 80% and 90% of Flec fighters have either joined the army or demobilised.
The city of Cabinda has been peaceful since the signing of the accord.
Correspondents say, however, that despite the deal many Cabindans would favour independence as they feel culturally and historically distinct from the rest of Angola.
Flec, which began fighting for independence from Portugal during the 1960s, continued to wage war against the Angolan government until last year.