Islam in Yemen dates back to about 630AD, when it was introduced into the region by Ali when Muhammad was still alive. It was during this period that the mosques in Janad (near Ta'izz) and the Great Mosque of Sana'a were built. Yemenis are divided into two principal Islamic religious groups: 55% Sunni and 45% Shia. The denominations are as follows: 55% primarily of the Shafi'i and other orders of Sunni Islam. 43% of the Zaidi order of Shia Islam, 2% of the Ja'fari and Western Ismaili orders of Shia Islam. The Sunnis are predominantly in the south and southeast. The Zaidis are predominantly in the north and northwest whilst the Jafaris are in the main centres of the North such as Sana'a and Ma'rib. There are mixed communities in the larger cities.