By Ibrahima Sylla

NOUAKCHOTT (Reuters) - Mauritanian forces hunting the killers of French tourists and government soldiers say they are unconvinced by a claim al Qaeda launched one of the attacks, even though analysts in the region say there is little doubt.

Last week's separate attacks have shaken the peaceful West African country as it prepares to host part of the Dakar Rally, which gives an annual boost to its nascent tourism industry.

A promise of 3,000 security personnel to ensure safe passage was enough for the rally's security chief, who has given the green light to its Mauritanian stages starting January 11.

But with hundreds of French tourists already switching trips to Morocco, Mauritanians are aware there is still time for a change of plan, should a serious al Qaeda threat be established.

Stages in neighbouring Mali were cancelled last year after French security services cited a threat from Algerian rebels.

"All indications about incidents in Mauritania pointed towards al Qaeda, whether the modus operandi or claims and statements by central and local leaders," said Moroccan political analyst Taj Eddine Husseini.

"Mauritania's reluctance to acknowledge al Qaeda's involvement may stem from its desire to protect the Dakar Rally passing through its territory and create an atmosphere of credibility and good feelings to see the rally through and shield its from fears of al Qaeda's threats," he said.

Last Monday three attackers, who authorities suspect are linked to al Qaeda, gunned down four French tourists and injured a fifth as they enjoyed a Christmas Eve picnic by the roadside in the south of the country, near the border with Senegal.

Gunmen killed three army soldiers three days later in the remote and sparsely populated north of the country, bordering Algeria and Morocco's breakaway territory of Western Sahara.

CLAIM

In an audio recording aired by Al Arabiya television, a spokesman said al Qaeda's North African branch had killed four soldiers late on Wednesday, but made no mention of the French.

Details in the statement differed from those given by the Mauritanian authorities, and the Gulf TV station said it could not verify the statement was indeed from al Qaeda.

Security sources in Mauritania's capital Nouakchott said al Qaeda was just one line of inquiry. They said the attackers may have been armed smugglers who traffic drugs, weapons and people over poorly policed borders deep in the Sahara.

The soldiers were shot dead by the occupants of two vehicles they were pursuing, who then made off with a heavy gun captured from the soldiers' vehicle.

"There is no doubt about al Qaeda's role in both killings of French tourists and slaying of the Mauritanian soldiers," said Mohamed Darif, an expert on Islamist groups in the Maghreb.

Security forces have detained at least seven people in relation to the killing of the French, but the three killers are still at large, possibly in neighbouring Senegal or Mali.

Mauritanian investigators say they are questioning the operator of a small boat, who they believe ferried the attackers across the Senegal river into Senegal.