* Peace talks between gov't, rebels start Tuesday evening
* Violence continues in north, south Yemen
SANAA, Aug 24 (Reuters) - Peace talks to cement a truce in north Yemen will start on Tuesday in Qatar between government officials and Shi'ite rebels, representatives on both sides said, despite a spike in violence killing seven people.
Yemeni delegations, made up of military representatives, are in Doha trying to turn a fragile northern ceasefire into a formal peace agreement with the help of Qatari mediators who helped seal a short-lived 2008 peace deal.
"Doha talks are to start today," a government official said, giving scant details. "The results will be announced when negotiators end their talks."
Yahya al-Houthi, a brother of the Shi'ite rebels' leader, is to take part in the talks, a rebel spokesman told Reuters.
Sporadic clashes have plagued the fractious northern region in spite of a ceasefire that has been bogged down in an on-and-off civil war since 2004.
Meanwhile, the country's south has seen an upsurge in al Qaeda attacks as well as a growing separatist revolt.
Fighting between the rebels and pro-government tribesmen killed at least four tribal fighters and three rebels in the northern town of Huth late on Monday, about 100 km (60 miles) north of Sanaa, and tribesmen took dozens of rebel fighters captive, a tribal official told Reuters.
Yemen reached a new truce with rebels in February to halt fighting that has displaced 350,000 people since 2004.
TALKS A SIDESHOW
Some Yemen analysts see the Doha talks as a sideshow to growing violence in the country's south, but others felt they would be a solid foundation for a long term peace, as the government seeks to turn its focus to fighting al Qaeda militants who pose a bigger global threat.
"I am very optimistic," said Abdul Ghani al Iryani, a Yemeni analyst based in Sanaa. "I think both sides, the government and the Houthis, are sincere in trying to negotiate a permanent ceasefire."
Yemen has come under increasing pressure to resolve domestic conflicts and focus on quashing a regional al Qaeda wing that regrouped in the Arabian Peninsula state last year and has launched attacks on Western, Saudi and Yemeni targets.
On the northern front, Iryani felt the peace talks may stumble if the government did not release imprisoned Houthis, the Shi'ite rebels who are identified by the clan name of their leader Abdul Malek al-Houthi.
The main demands from the rebel side have been the government release of prisoners, while Houthis were expected to relinquish their arms as well as control of the region to the state.
Both sides have accused the other of bringing the region to the brink of war by not living up to their obligations.
"So far the government has been resistant and has not released the Houthi prisoners. That's a sticking point that might destroy the chances of this effort," he said. (Additional reporting by Mohammed Ghobari in Sanaa and Regan E. Doherty in Doha; Writing by Erika Solomon; Editing by Nina Chestney)
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