MECCA, Saudi Arabia — Leaders from more than 50 Muslim countries promised Thursday to fight extremist ideology, saying they would reform textbooks, restrict religious edicts and crack down on terror financing.

Kings, heads of states and ministers closed a two-day summit in Islam's holiest city, Mecca, that had been convened to address terrorism, seeking to counter criticism that the Islamic world has done little to confront extremism.

"The Islamic nation is in a crisis. This crisis does not reflect on the present alone, but also on its future and the future of humanity at large," said the final statement of the gathering. "We need decisive action to fight deviant ideas because they are the justification of terrorism."

In the declaration, the countries of the Organization of the Islamic Conference promised to "change national laws to criminalize financing and incitement" as well as purge extremist ideas from school curriculums.

It also underlined that "fatwas" — or Islamic religious edicts — must only be issued by "those who are authorized," an effort to rein in edicts by clerics who denounce other Muslims and allow their killing.

"It is now up to every Muslim government to implement the measures, God willing," Saudi Foreign Minister Prince Saud al-Faisal said at a news conference.

Leaders of about 40 countries were participating in the meeting of the Organization of the Islamic Conference, with the remaining OIC members represented by ministers.

Saudi Arabia has cracked down on al-Qaida militants there since a wave of attacks in early 2003, and King Abdullah has taken gradual steps to clamp down on militant preachers in his country, the homeland of al-Qaida leader Osama bin Laden and 15 of the 19 suicide hijackers in the Sept. 11, 2001 terror attacks in the United States.

Jordan's King Abdullah II also played a leading role at the summit, pressing for strong language against terrorism and extremist ideology after his country was hit by its worst ever terror attack last month, a triple suicide bombing at Amman hotels that killed 60 people.

Among noted absentees were Syrian President Bashar Assad, Algerian President Abdelaziz Bouteflika — hospitalized in France — and Turkish Prime Minister Recep Tayyip Erdogan.