Guinea's security forces have detained the son and brother-in-law of late President Lansana Conte in a drug-smuggling investigation, police and security officials said on Tuesday.

The detentions were a new challenge to Conte's family since soldiers led by Captain Moussa Dadis Camara seized power following the president's death in December.

Human rights activists welcomed the arrests as a sign of a return to the rule of law in the country, a major bauxite producer, but also said the military junta should not use the anti-drug crackdown to settle political scores.

Conte's son Ousmane, an officer in Guinea's army, was detained late on Monday and taken to the main military camp in the capital Conakry, a senior police official told Reuters.

Ousmane was arrested after Saturin Bangoura, the brother of the late president's wife Henriette, confessed on state television on Monday to receiving tens of thousands of dollars in cash and goods from a "Colombian partner".

"He (Ousmane Conte) was named by those who had already been arrested, so he had to be detained," said a second senior police officer, who confirmed the arrest but asked not to be named.

Like other West African countries, Guinea has become a transit point for Colombian cocaine being smuggled for sale in Europe and elsewhere.

RIGHTS WORRIES

Drug dealers have targeted weak states in West Africa, where analysts say senior political and security officials have collaborated with Latin Americans seeking new smuggling routes.

Guinean authorities detained four senior police officials last Friday in a widening probe into drug smuggling, which Camara's National Council for Democracy and Development (CNDD) junta has pledged to tackle since taking power.

Guinea's military rulers have been criticised for their coup and are under pressure to restore civilian rule by organising elections. They have promised polls before 2010.

After widespread allegations of the criminalisation of the state during Conte's 24-year rule, analysts and rights groups have welcomed some of the steps to restore order.

But there are concerns that the campaign could also be counter-productive if used for extortion and racketeering.

"The good news is that the CNDD is taking steps to arrest erstwhile untouchables including policemen and members of the former first family implicated in drug trafficking," said Corinne Dufka, Human Rights Watch's West Africa researcher.

"The bad news is that by detaining suspects in a military camp, using the crackdown as a pretext to commit criminal acts against ordinary Guineans, and, at times, using excessive force, they are undermining the rule of law in the process," she said.

Several members of the CNDD, including a newly-appointed minister, have been arrested since the junta took power and accused of fomenting instability.