Central Maghreb from Achir to Bejaia, Constantine.

In recognition of his loyalty to the Fatimids, the founder of the Zirid dynasty, Ziri ibn Manad, was authorised around AH 323 / AD 935 to found the town of Achir on the edge of the Tellian Atlas. The town's perfectly central position between the Tell and the High Plateaux made it an active capital and a place of commercial and cultural exchange.
To consolidate his power over the region and to provide outlets to the sea, Buluggin, the son of Ziri, founded three more towns: Miliana, Lemdia (modern-day Médéa) and al-Djazaïr (Algiers) before taking control of Ifriqiya and Central Maghreb as a vassal to the Fatimids. The Zirids settled in Mansuria, the former capital of the Fatimids, entrusting Achir to their Hammad cousins. These latter made their desire for independence clear when they set up a rival principality whose capital, Qal'at Bani Hammad, was founded in 397 / 1007 in the Hodna mountains near to the town of Msila to the southeast of Algiers. There the Hammadids erected many large buildings whose artistry and refinement would later inspire the builders of Andalusian Spain.
The war between the Zirids of Ifriqiya and the Hammadids of Central Maghreb, who were cousins, lasted until 433 / 1042, when their heirs were able to make peace and settle in their two capitals: Achir and Qal'at. The entire region then enjoyed a period of prosperity that was recognised by all contemporary writers.
In 439 / 1048, the Zirids broke off their bond of vassalage with the Fatimids of Cairo, and the region became independent. This political break was compounded by a religious one facilitated by Maghreb's traditional attachment to Malekism, and the Fatimid Shi'a rite made way for Malikite Sunni orthodoxy. In retaliation, the Fatimid caliph of Cairo sent the Arab tribes of Bani Hilal and Banu Sulaym to subdue Maghreb, and they swept through the region from 441 / 1051.