DUBAI, July 4 (Reuters) - Qatar's new emir congratulated Egypt's Adli Mansour on Thursday after he was sworn in as an interim leader following the ousting of Islamist President Mohamed Mursi, an ally of the Gulf Arab country, state news agency QNA reported.

Qatar was alone among Gulf Arab states in celebrating the 2011 Arab Spring revolt that toppled former President Hosni Mubarak, a foe of Iran and a longtime ally of the hereditary states that sit on nearly a quarter of the world's oil reserves.

The small, energy-rich country provided billions of dollars in aid to Egypt following the ousting of Mubarak.

QNA said the emir, Sheikh Tamim bin Hamad Al Thani, "sent a cable of congratulations" to the head of Egypt's Supreme Constitutional Court on the occasion of his taking the oath as an interim president.

The agency and Qatar-owned al Jazeera television had earlier quoted a foreign ministry source as praising the Egyptian army's role in safeguarding Egypt's national security and said the Gulf Arab state respected the will of the Egyptian people.

Qatar has been a major financier of the Islamist groups around the Arab World, including Egypt's Brotherhood. In addition to financial aid, the Gulf state had donated fuel cargoes over the past year to support shortages in the country.

Qatar's allies in the six-member Gulf Cooperation Council, including Saudi Arabia, the United Arab Emirates, Kuwait and Bahrain had earlier sent congratulatory messages to Mansour. (Reporting by Amena Bakr and Mahmoud Habboush, Editing by Sami Aboudi and William Maclean)