UPDATE 2-Senegal opposition urges more 'resistance' after riots
* Capital Dakar calm after overnight riots, security raised
* Opposition says to make country "ungovernable" if Wade seeks new term
* Govt says security forces committed to preserving peace (Adds N'dour incident)
By Diadie Ba
DAKAR, Jan 28 (Reuters) - Senegal's opposition said on Saturday it would make the country "ungovernable" if President Abdoulaye Wade insisted on running for a third term in elections next month, raising the spectre of renewed riots in West Africa's most peaceful nation.
One policeman was killed during protests late on Friday, in which demonstrators threw rocks, overturned cars and burned tyres and security forces fired tear gas, after the country's top court said Wade had the right to seek a new term.
Calm returned to the capital Dakar by Saturday but security was boosted around the presidential palace, where truckloads of police in full riot gear were deployed, armed with tear gas grenade launchers and truncheons.
"Abdoulaye Wade has declared war on the people," Amath Dansakho, the head of the PIT party and member of the M23 opposition activist group, told reporters following a meeting with other political and civil society leaders.
"The decision that we have just made will prove to Wade that this is a country of free people. We will render the country ungovernable," he said.
Friday's clashes came after Senegal's top legal body validated the candidacy of 85-year-old Wade and 13 rivals for the Feb. 26 vote, but turned down the presidential bid of world music star Youssou N'Dour, saying he did not have the required 10,000 signatures of support.
Wade's rivals say the constitution sets an upper limit of two terms on the president. But Wade, who came to power in 2000 and was re-elected in 2007, has argued his first term pre-dated the 2001 amendment establishing the limit.
M23 said in a press release on Saturday the court's decision was a "constitutional coup, and a prelude to what will be an electoral coup" and called on Senegalese across the country to resist Wade's re-election bid.
Senegal's interior ministry said on Saturday that a policeman was killed during Friday's clashes, which began after protesters that had gathered in a public square attempted to march towards the presidential palace.
The policeman "was gravely injured in the head by a brick that had been thrown, and he succumbed shortly afterward," the ministry said in a press release, adding security forces remained committed to preserving the peace.
A leading human rights activist and vocal critic of Wade, Alioune Tine, told Reuters by text message on Saturday afternoon that he had been arrested by Senegal's criminal investigation unit, but he could not give further details.
Police shoved N'dour and knocked his spectacles off his face when he attempted to visit Tine at the police station late on Saturday, his spokesman Adama Sow said.
Wade had appeared on state television late on Friday appealing for calm and promising free and fair polls.
Senegal is the only country in mainland West Africa to have not had a coup since the end of the colonial era. February's poll, and a possible run-off a few weeks later, are seen as a test of social cohesion in the predominantly Muslim country.
Critics say that Wade, who spent 26 years in opposition to Socialist rule, has done nothing during his 12 years in power to alleviate poverty in a country where formal employment is scarce, and has dragged his heels on tackling official graft.
Wade points to spending on education and infrastructure projects such as roadbuilding as proof of progress towards turning Senegal into an emerging market country and a trade hub.
His candidacy has raised eyebrows abroad. The senior U.S. State Department official for Africa, William Fitzgerald, told French RFI radio that Wade's candidacy was "a bit regrettable".
Rival presidential hopeful Amsatou Sow Sidibe called on Wade to withdraw his candidacy voluntarily. "Peace and tranquility in Senegal depends on it," she told Reuters by telephone.
Reuters reporters late on Friday saw youths set fire to tyres and overturn cars in Dakar. Protests were also reported in the towns of Thies, Mbour, and Kaolack, where state radio said the local headquarters of Wade's liberal PDS were burned down. (Writing and additional reporting by Richard Valdmanis; Editing by Myra MacDonald)