BAMAKO, May 23 (Reuters) - About 20 Malian soldiers were killed and 30 wounded in a failed attempt by government forces to retake the Tuareg separatist stronghold of Kidal this week, the defence minister said.
The fighting, the worst since the government and separatist groups signed a preliminary peace agreement last year, threatens to sink struggling negotiations to end a long cycle of Tuareg uprisings and plunge Mali's desert north back into war.
"There were killed and wounded on both sides. We have around 30 wounded ... and then we have some 20 dead unfortunately," Soumeylou Boubeye Maiga said in an address broadcast on state television late on Thursday.
The army launched Wednesday's assault on Kidal after clashes erupted at the weekend during a visit to the town by recently appointed Prime Minister Moussa Mara.
Eight civilians, including six government workers, were killed when the separatists attacked the local governor's office. Another 32 civil servants taken hostage by the rebels were later released.
The government has accused the separatists, including the National Movement for the Liberation of Azawad (MNLA), of renewing their former alliances with al Qaeda-linked Islamist groups.
"The MNLA was supported by its traditional allies," Maiga said.
Mali was plunged into chaos in 2012 after Tuareg independence fighters teamed up with armed Islamist groups to seize the north following a coup in the capital.
When they were sidelined by the better-equipped Islamists, the separatists broke with their allies. A French-led military operation then drove the Islamists back last year.
The MNLA says it controls at least seven northern towns in addition to Kidal after it said government troops either abandoned their positions and sought refuge at the camps of the U.N. peacekeeping mission, MINUSMA, or fled south.
While neither the U.N. nor French forces in Mali intervened to halt this week's clashes, MINUSMA said it had protected 62 Malian soldiers in its base in Kidal and another 290 troops in the town of Aguelhok.
The mission said it had airlifted a total of 61 wounded Malian soldiers to the northern city of Gao and the capital Bamako on Thursday. (Reporting by Tiemoko Diallo and Adama Diarra; Writing by Joe Bavier; Editing by Janet Lawrence)