* Eight soldiers killed, 25 wounded in clashes on Saturday
* Violence threatens to sink peace talks between govt, rebels
* Tuareg rebels claim control of northern town (Updates tolls for dead and injured, adds U.N. statement)
By Adama Diarra
KIDAL, Mali, May 18 (Reuters) - Mali's prime minister said his country was at war with Tuareg separatists after the rebels attacked a northern town he was visiting, killing eight soldiers and abducting around 30 civil servants.
Some shooting had already broken out before Prime Minister Moussa Mara's arrival in Kidal early on Saturday and he was forced to take shelter in an army base as rebel fighters attacked and seized the regional governor's office.
Clashes continued throughout the day with sporadic shooting eventually easing during the night.
"In light of this declaration of war, the Republic of Mali is henceforth at war," Mara told a Reuters reporter inside the base overnight.
The prime minister was visiting Kidal for the first time since his appointment last month to revive long-delayed talks with northern armed groups.
Mali, a former French colony, was thrown into turmoil in 2012 when al Qaeda-linked Islamists took advantage of a Tuareg-led rebellion and seized control of the country's north.
A French-led military operation, known as Serval, drove back the Islamists last year but now the Mali government's focus has turned back to the Tuareg rebels.
A spokesman for the MNLA rebel group claimed control of the town of Kidal on Sunday. During the day Mara moved on from Kidal to another northern town, Gao.
The clashes, potentially the worst pitting the government against Tuareg rebels since the French intervention, now threaten to sink efforts to find a peaceful solution to the long cycle of rebellions in the West African nation's desert north.
The government and a grouping of armed groups, which broke with the Islamists ahead of the French offensive, signed an agreement last year promising to hold talks over autonomy.
MINUSMA, a nearly 13,000-strong United Nations peace-keeping mission, is rolling out but is not yet at full strength.
Mara poured criticism on both the French and U.N. forces for allowing the attack to take place.
"You were witnesses today to the more than passiveness of these forces," he said. "The very least we'd expected from MINUSMA and Serval was that they'd ensure the governor's office wasn't attacked."
In a statement on Sunday, MINUSMA said 21 U.N. police officers were injured in the clashes while providing security for the prime minister. Two suffered from serious gunshot wounds. However the peacekeeping mission did not say who was believed to have started the clashes.
"These acts constitute a serious violation of the preliminary agreement and hamper efforts aimed at bringing peace and security to the regions of the north, particularly Kidal."
REBELS IN CONTROL?
"During the clashes, the Malian armed forces recorded eight dead and 25 wounded, while 28 dead and 62 wounded were counted on the side of the aggressors," the Defence Ministry said in a statement. The figures given by the government could not immediately be independently verified.
A Malian military source said Saturday's gun battle erupted after MNLA fighters in two trucks attacked an army checkpoint in front of the governor's office. A Reuters journalist travelling with Mara saw the body of one dead soldier.
Regional governor Adama Kamissoko told Reuters that three of the worst injured soldiers had been evacuated by helicopter. He said MNLA fighters had kidnapped the civil servants, gathered at the governor's office to meet the prime minister.
A spokesman for the MNLA said the army attacked first, opening fire on the group's barracks following pro-independence protests in the town.
"We've taken about 40 prisoners, including high-ranking military officers and civil servants. They're all safe and sound and doing well," Attaye Ag Mohamed told Reuters by telephone from the town. He said there had been no fighting on Sunday.
"The town is completely secured by us...The army are back inside their base. If they attack us, however, we'll fight back," he said. (Additional reporting by Tiemoko Diallo; Additional reporting and writing by Joe Bavier; Editing by Andrew Heavens and Stephen Powell)