A Malian military official confirmed the deaths, saying that "it was terrorists from Al-Qaeda in the Islamic Maghreb who were responsible for the attack...."
"Our base in Gargando was attacked early Saturday by Islamist terrorists," Oumar Ag Keling, a member of the Tuareg-led Congress for Justice in Azawad, told AFP.
Gargando is a small town about 170 kilometres (106 miles) west of the historic city of Timbuktu.
"They killed four of our fighters, as well as the village chief," Keling said, adding that the jihadist rebels were "of many nationalities, according to the documents found at the scene".
A Malian military official confirmed the deaths, saying that "it was terrorists from Al-Qaeda in the Islamic Maghreb who were responsible for the attack, because the CJA was becoming a powerful force in the region".
For more than a month, the CJA -- formed in October 2016 to gain a bigger voice in the peace process for the Tuareg ethnic community of Kel Ansar, in Mali's northwest -- has opposed the installation of interim local authorities in Timbuktu, a central part of a peace deal signed in 2015.
The rebels signed the deal along with the government and pro-Bamako militias in the hopes of bringing stability to the north, the cradle of several Tuareg uprisings and a sanctuary for Islamist fighters.
Under the agreement, interim authorities will represent the inhabitants of Mali's five northern regions until security improves so that local elections can be held.
Implementation of the peace accord however has been piecemeal and insurgents who refused to sign the deal are still active across large parts of the country.
Mali's north fell under the control of jihadist groups linked to Al-Qaeda in 2012 who hijacked the rebel uprising, though the Islamists were largely ousted by a French-led military operation in January 2013.
In another attack, a member of a pro-government group was killed on Friday in the northeast village of Anefis, according to an international security source, but they could not identify the perpetrators.
Mali's jihadists did not sign the 2015 peace deal that aimed to quell separatist uprisings in the north and have continued to wreak havoc.
In a separate development, President Ibrahim Boubacar Keita appointed defence minister Abdoulaye Idrissa Maiga, 59, as prime minister, replacing Modibo Keita who had been in office since January 2015, according to a decree issued Saturday night.
Maiga, who was the president's campaign manager during the 2013 election, will meet Sunday with several political parties on the formation of a new government, according to his entourage. He is Keita's fourth prime minister.