* Senegal detains Mauritanian, Malian over militant ties
* US official sees "growing terrorist presence" in Africa
* Washington: reforms must accompany Mali military ops
By Diadie Ba
DAKAR, Feb 15 (Reuters) - Senegal has detained a Mauritanian and a Malian for suspected terrorist links, its government said on Friday, and a top U.S. defence official called for international teamwork to counter a growing presence of al Qaeda and its allies in Africa.
The United States and African governments are backing a five-week-old French military campaign against Islamist rebels in Senegal's neighbour Mali, calling it a blow against jihadists who threaten attacks in Africa and elsewhere.
After driving the bulk of the rebels from north Mali towns such as Gao and Timbuktu, French, Malian and African troops are pursuing the insurgents in the remote mountainous northeast where they are thought to be holding French hostages.
But the French are struggling to secure the liberated areas from the threat of jihadist suicide bombers and guerrillas who have struck at Gao, raising fears al Qaeda and its allies could attempt reprisal attacks in the wider region.
A Senegalese justice ministry official said the Mauritanian and Malian suspects were arrested this week by local gendarmes at Velingara, more than 600 km (375 miles) southeast of the Senegalese capital Dakar.
"They are in custody for criminal conspiracy in collusion with terrorist organisations, aimed at undermining the country's military situation and its economic interests," Macoumba Mbodj, an adviser at the ministry, told Reuters.
Mbodj said an investigation was continuing and withheld further details. He would not comment on Senegalese media reports saying the detained Mauritanian was a member of al Qaeda who was trying to recruit young men to fight in Mali.
In testimony before the U.S. House of Representatives Foreign Affairs Committee in Washington on Thursday, senior U.S. officials said the threat posed by al Qaeda's North African wing AQIM and allied groups extended well beyond Mali and would require long-term international efforts to "neutralise".
"This is part of a growing terrorist presence in the region that threatens U.S. citizens, interests and partners," said Amanda Dory, U.S. Deputy Assistant Secretary of Defence for African Affairs.
Senegal, which has sent several hundred troops to join a U.N.-backed African military force for Mali that is still being deployed behind the French advance, has tightened security on its southeast border with its West African neighbour.
France has said it wants to begin withdrawing its 4,000 troops from Mali in March, but risks getting sucked into a tough counter-insurgency war in its ex-Sahel colony.
French warplanes this week hit Islamist rebel bases and supply lines in Mali's desert northeast, especially in the Aguelhok region, the French defence ministry in Paris said. It said six buildings and a storage zone, as well as a training camp of "terrorist groups", had been destroyed.
EXTREMIST "NETWORK" IN AFRICA
In her Washington testimony, Dory pointed to an attack last year in Benghazi, Libya that killed the U.S. ambassador and three other Americans, and to a deadly January raid by jihadists on the In Amenas natural gas plant in Algeria.
She said AQIM had the ability to attack western interests, and target or kidnap westerners for ransom.
Dory cited danger from what she called "a network of violent extremist organizations in Africa, from Egypt to Libya to Somalia to Nigeria", describing a risk of "cross-fertilization and cross-pollination between affiliated groups".
"The threat is dynamic and evolving and our efforts to counter it must be as well."
U.S. Assistant Secretary of State for African Affairs Johnnie Carson said the Mali intervention should be accompanied by reforms to foster good governance and economic development.
"Terrorists prey upon fragile states," Carson said, and the success of the French-led mission would be "fleeting without a democratic and credible government that is responsive to the needs of Malians".
Mali's interim government, formed after a March 22 coup that mired the nation in chaos and led to the north's occupation by rebels, said on Thursday it would hold a presidential election on July 7, and legislative elections two weeks later.
Coup leaders have continued to meddle in state affairs, increasing foreign calls for a legitimate civilian government.
In Mali's recaptured north, pro-autonomy Tuaregs - whose revolt last year was hijacked by the radical Islamists - are demanding direct talks with the central government in Bamako.
Carson said that while there could be no dialogue with groups supporting "terrorism", the legitimate political, social and economic grievances of indigenous communities in northern Mali should be addressed. (Additional reporting by John Irish in Paris, and Pascal Fletcher in Dakar.; Writing by Pascal Fletcher; Editing by Mark Heinrich)