As an example one could mention the De Vecchi’s governorship (1923–1928), when thousands of indigenous people were subjected to forced labor. In the same period, the [Fascist] governor undertook a campaign of aggressive military expansion marked by a violent repression against the civilian population.

Moreover, and notwithstanding the attempt to ignore or try to explain away evidence of the atrocities occurred, it is a fact that at the end of 1935 Italy extensively used poison gas in Africa. Thirty‐six tons of mustard gas were apparently sent in Somalia in September 1935. In addition, in the very same year, a concentration camp was built at Danane, not far [south] from Mogadishu.

Indeed, the acts of violence against civilians date back to before the advent of Fascism. In the early twentieth century, the [Regio Esercito] wiped out entire populations stationed on Somali territory, for instance the Bimàls and Majerteens. In 1905, slavery was formally outlawed, but in practice widely tolerated for many years.

In fact, the Benadir officials’ practice to purchase female slaves or coerce local women to be their mistresses has not been particularly obstructed when the Italian government asserted its direct administration of Somalia.

[…]

Although not much material is available, it seems beyond doubt that forced labour was a widespread practice both in liberal and fascist Italian colonialism. Mostly, this labour, based on the exploitation of indigenous people, was not needed for the military occupation, but was destined for the development of the agricultural sector and aimed at favouring the installation of Italian agrarian companies.

As discussed in Abdisalam M. Issa‐Salwe’s The Collapse of the Somali State, Cesare Maria De Vecchi and his crew commenced a reconquest of Somalia which lasted from 1925 to 1928. To give just one example of his exploits:

While in Africa, De Vecchi ordered the extremely bloody action by Fascist squads against Somali dissidents on 28 October 1926 that caused about one hundred deaths.

Concerning the Danane concentration camp:

of the 6,500 Ethiopians and Somalis who passed through the camp between 1936 and 1941, 3,175 died either through poor or insufficient food, malaria, enterocolitis, lack of hygiene, the unhealthy climate and salinated wells.

(Details here, including on how some survived.)

Ian Campbell’s The Addis Ababa Massacre has a great deal of information on this camp, but for brevity’s sake I shall quote only one paragraph:

For most of the prisoners at Danane there was never any imputation that they had done anything wrong. They were not convicts, for they had never been convicted of any offence. Thus Danane was not officially a death camp, but, since the captives there were sentenced to life imprisonment, it was clearly intended that they would all die at Danane, sooner or later.

Several officials of the Italian administration, which was well known to have been riddled with corruption, had lucrative banana concessions and sugar‐cane plantations at a project known as Genale, and ran them using forced labour from Danane.

(Emphasis added in all cases.)

Further reading: The "Historic Sins" of Colonialism in Somalia (a perspective from a Somali).