Buses are seen ablaze during clashes between Islamists and their opponents in Egypt's northern seaside city of Alexandria on Dec. 21, 2012. The clashes came one day ahead of the second round of the country's constitutional referendum. (Xinhua/Wissam Nassar)

An Egyptian man is wounded during clashes between Islamists and their opponents in Egypt's northern seaside city of Alexandria on Dec. 21, 2012. The clashes came one day ahead of the second round of the country's constitutional referendum. (Xinhua/Wissam Nassar)

Egyptian riot police try to quell clashes between Islamists and their opponents in Egypt's northern seaside city of Alexandria on Dec. 21, 2012. The clashes came one day ahead of the second round of the country's constitutional referendum. (Xinhua/Wissam Nassar)

Buses are seen ablaze during clashes between Islamists and their opponents in Egypt's northern seaside city of Alexandria on Dec. 21, 2012. The clashes came one day ahead of the second round of the country's constitutional referendum. (Xinhua/Wissam Nassar)

Egyptian riot police try to quell clashes between Islamists and their opponents in Egypt's northern seaside city of Alexandria on Dec. 21, 2012. The clashes came one day ahead of the second round of the country's constitutional referendum. (Xinhua/Wissam Nassar)

Buses are seen ablaze during clashes between Islamists and their opponents in Egypt's northern seaside city of Alexandria on Dec. 21, 2012. The clashes came one day ahead of the second round of the country's constitutional referendum. (Xinhua/Wissam Nassar)