Ukraine Ukraine's constitutional court ruled that recently adopted electoral changes were unconstitutional, in a decision that threw into doubt the legitimacy of a rerun presidential vote set for the following day. Iraq At least seven people, including the suicide bomber, were killed and 19 wounded when an explosives-rigged fuel tanker blew up on Christmas Eve in western Baghdad, police and an AFP correspondent said. Vatican Pope John Paul II celebrated the traditional midnight mass at the Vatican with special prayers for peace in the region of the Middle East where Jesus Christ was born. Indonesia Christians in Indonesia, the world's largest Muslim-populated country, flocked to churches to celebrate Christmas under tight security following warnings of possible terrorist attacks. Mideast Muslims and Christians united in the hope that the festive season will herald a new dawn after four years of violence, attending midnight mass in Bethlehem, the birthplace of Jesus Christ. US The European-made space probe Huygens headed for a historic up-close encounter with Titan, the only celestial body of the Solar system with an atmosphere resembling that of Earth, after successfully separating from the US spacecraft Cassini. Taiwan Frenchman Alain Robert defied bad weather to set a personal record by climbing the world's tallest building, Taipei 101, in four hours. Liberia For the first time in the wake of two successive civil wars that claimed more than 200,000 lives, the west African state of Liberia was celebrating Christmas in peace -- even though many could barely find the funds to buy presents for their children.