Yemen, officially the Republic of Yemen, is a sovereign state in West Asia. Located in the southern Arabian Peninsula, it borders Saudi Arabia to the north, Oman to the northeast, and the Indian Ocean to the south, sharing maritime borders with Eritrea, Djibouti and Somalia across the Horn of Africa. Covering roughly 528,000 square kilometres, with a coastline of approximately 2,000 kilometres, Yemen is the second largest country on the Arabian Peninsula. Sanaa is its constitutional capital and largest city. Yemen's estimated population is 34.7 million, comprised mostly of Arab Muslims. It is a member of the Arab League, the United Nations, the Non-Aligned Movement and the Organisation of Islamic Cooperation.