Leaders stressed the Egyptian novelist's commitment to peace and dialogue between civilisations, while friends and artists praised the pioneering nature of Mahfuz's works and his simple kindheartedness.
United Nations Secretary General Kofi Annan, who is currently on a Middle East tour, "is saddened by the passing of this very eminent writer," his spokesman Stephane Dujarric said in New York.
"It is a great loss for the Arab world, and the world of literature as a whole for a man who has brought so much and done so much for Arab culture," the spokesman added.
"A prominent figure of world literature, a man of peace, tolerance and dialogue has passed away," French President Jacques Chirac said in a statement.
Tribtue from Bush
French Prime Minister Dominique de Villepin said Mahfuz's work and life "will remain a constant encouragement and an example of refusing to bend to intimidation".
US President George W. Bush said "the writings of this extraordinary author of novels, short stories and film scripts transcend all stereotypes and show the deepest insight into the lives of Egyptians and of all mankind."
Mahfuz "was an exceptional writer, an enlightened and creative thinker, an author who brought Arab culture and literature to the world's attention," a statement from Egyptian President Hosni Mubarak's office said.
His novels represented "values that are common to the whole of humanity and his works helped values of tolerance, opposed to extremism," the statement added.
In Berlin, a statement by Foreign Minister Frank-Walter Steinmeier said Germany mourns "a great thinker and extraordinary writer" who "many times used the force of words to clamour for justice, liberty, love and the well-being of all people on this planet".
Mahfuz, who won the Nobel prize for literature in 1988, died on Wednesday of heart failure, several weeks after his condition abruptly deteriorated.
Mahfuz was celebrated for universal reach of his novels, including the celebrated Cairo Trilogy.
His career spanned 70 years and his position as the patriarch of modern Arab literature made him one of the most prominent writers of the past century.
Israel sends condolences
"The death of Nagib Mahfuz is a huge loss for the Arab world and the entire world. His works spread way beyond national boundaries and will continue to influence future generations," Egyptian Culture Minister Faruq Hosni said.
In a telegram to Hosni, Israeli Culture Minister Ophir Pines called Mahfuz "a great writer" and recalled his "support for the peace process" with Israel and "the price he had to pay" -- a reference to attacks against him in his home country.
"With the death of the late author, we have lost a great creative mind and one of the most prominent pillars of Arab literature," Jordan's King Abdullah II said in a message of condolence.
Egyptian writers mourn
Abdou Diouf, the secretary general of the International Organisation of the French-speaking world, also paid homage to "a great novelist, the first Arab laureate of the Nobel Prize for Literature and the only one to this day, who made a mark on his times with his works and his convictions."
Virtually every artist in Egypt looked up to Mahfuz and messages of condolence poured in from disciples, friends and fellow writers who have been influenced by the late novelist's writings.
Sonallah Ibrahim, probably the most prominent Egyptian in Mahfuz's absence, told AFP "Mahfuz should be considered the master of the Arab novel. Each one of his novels was a new experience."
"Nagib Mahfuz is to Arab fiction what the pyramids are to Egypt," he said.
The author's entourage voiced unanimous admiration for Mahfuz, who was notorious for being a very disciplined writer, mourning a dedicated friend and an unrivalled source of inspiration.
"There is no doubt he was one of the greatest in the Arab world and his Nobel prize (in 1988) was really deserved. On a personal level, he had a simple manner and was very kind to people," said novelist Mohammed al-Bosati.
"Nagib Mahfuz loved life and for him, writing and creating were a way to fight against oblivion and death," said Yusef al-Qaid, a novelist and close friend.