At least 17 people were killed after an explosion ripped through an apartment block in a Ukrainian Black Sea resort town of Yevpatoria.
Ukrainian President Victor Yushchenko declared December 26 a day of national mourning.
Yushchenko and Prime Minister Yulia Tymoshenko arrived together at the site today.
Tymoshenko, citing preliminary information, told reporters in the regional capital Simferopol that the accident was caused by an explosion of oxygen or acetylene cylinders in the building's basement.
Russian President Dmitry Medvedev expressed condolences over the blast, saying the country's Black Sea fleet was ready to assist in a rescue operation.
Compiled from agency reports