Mali's justice ministry announced Thursday it had opened an investigation into the deaths of 17 soldiers killed in an attack on their base, as Malians observed the first of three days of mourning.

The government declared a state of emergency after two groups -- one jihadist, the other ethnic -- both claimed to have carried out the raid on the military camp on Tuesday, which also left dozens wounded.

"A preliminary investigation has been opened by the chief prosecutor for terror offences," the ministry said in a statement, calling on Malians to "inform the judicial authorities of anything that can help to advance our inquiries."

A previous state of emergency in place since April had only been lifted the week before.

Malian jihadist organisation Ansar Dine claimed responsibility for the attack, along with the recently-founded National Alliance for the Protection of Peul Identity and Restoration of Justice (ANSIPRJ).

The military camp massacre in Nampala, central Mali, was the latest in a series of assaults on security forces in Mali, and was condemned as a "coordinated terrorist attack" by the government.

Flags flew at half mast outside many buildings in the capital Bamako on Thursday, as President Ibrahim Boubacar Keita travelled to visit the wounded and pay tribute to the dead in Segou, the capital of the region where the attack happened.

Mali has seen repeated violence since it fell under the control of Tuareg-led rebels who allied with jihadist groups linked to Al-Qaeda in 2012, including Ansar Dine.

Attacks are now becoming more frequent in the country's centre, close to its borders with Mauritania, Burkina Faso and Niger, both from criminal and jihadist elements.

Although Islamists were largely ousted by an ongoing French-led military operation launched in January 2013, sporadic attacks from desert hideouts are common.