At least three UN soldiers were killed and 30 others injured Friday after a militant group fired rockets at a UN peacekeepers camp in Kidal, northern Mali, Olivier Salgado, MINUSMA spokesperson, told Anadolu Agency."The death toll is provisional because we recorded several serious injuries," said the UN official reached by phone."Several rockets were fired this morning at around 0650GMT. There were also several material damages," Salgado said.A Malian security source said, told Anadolu Agency that two of the peacekeepers killed belonged to the Guinean contingent of the UN peacekeeping mission in Mali. The identity of the third soldier is not known for now, he added.Calm returned to the city after more than two hours of gun shots, residents told Anadolu Agency.The attack took place as Mali is waiting for the arrival of German President Joachim Gauck to the country."The attack could be a signal against Germany which has promised to send more than 600 soldiers to Mali to strengthen its presence in the country," according to a western military attaché reached by Anadolu Agency in Bamako."Some armed groups in the north have officially declared war on what they call the occupation forces, in this case the MINUSMA and Barkhane (French forces) and the Malian armed forces," said the military attaché, who requested anonymity for diplomatic reasons.The MINUSMA consist of 9,142 soldiers, according to latest UN figures.Recent months have seen sporadic militant attacks on UN peacekeepers and Malian army personnel.Last Friday, an attack had targeted a base of the Nigerian police Minusma Timbuktu, northwestern Mali.A Malian military, as well as at least four assailants were killed, according to the Malian authorities. The attack was later claimed by Al-Qaeda in Islamic Maghreb (AQIM).On Dec. 14, a camp of the UN Mission in Gao, northern Mali, was targeted by gunmen but no casualties was reported.On Nov. 28, gunmen attacked a MINUSMA base in Kidal killing three people (two Guinean peacekeepers and a civilian) and 20 others injured, according to the UN mission in Mali.The attack was claimed on the same day by a militant group called Ansar Dine.Several militant groups are still rampant in northern Mali despite the presence of UN and French forces since 2013.The Malian government and some Tuareg rebel groups signed a peace agreement in June 2015.