United Nations Secretary General Kofi Annan "expressed deep sadness over the deaths and devastation."

"The secretary general is deeply saddened by the loss of life and large-scale destruction wrought... along the United States Gulf Coast," his spokeswoman Marie Okabe said.

"He extends his sincere condolences to all the victims and their families."

The fierce storm has left in its wake a still unknown death toll. In Mississippi alone it is estimated 125 people lost their lives in what French President Jacques Chirac called "terrible days" for Americans.

"In these painful circumstances, I wish to express the solidarity of the French people and my sincerest condolences for the tragic disappearance of so many of your compatriots," Chirac said in a letter to his US counterpart, George W. Bush, whom he addressed as "dear George".

Pope Benedict XVI expressed sadness at the "tragic consequences" of the fierce hurricane that walloped coastal communities in Louisiana and Mississippi with 225-kilometer-per-hour (140-mile-per-hour) winds and torrential rain as it made landfall on Monday.

In and around New Orleans, the city known as a mecca for American jazz, close to a million people have been evacuated but officials said several hundred thousand were still trapped as more than 80 percent of the low-lying city was underwater.

In offering prayers for the grieving families, the leader of the Roman Catholic Church also paid tribute to "the rescue workers and all involved in providing assistance to the victims of this disaster," the pope's message read.

Britain's Queen Elizabeth II voiced sorrow in a message to Bush.

"I was deeply shocked and saddened to learn of the deaths and injuries caused by Hurricane Katrina, and the scale of the damage and destruction now becoming apparent across the southern states," said the message made public by Buckingham Palace.

"My sympathy goes to you and the people of the United States, especially to the families of those who have lost their lives, to the injured and to all who have been affected by this terrible disaster."

An offer of support for the US rescue operation came from Russia's emergency situations ministry, which said it had two transport planes at the ready, together with rescuers, search helicopters and equipment for autonomous operations in a disaster zone.

Saudi Arabia's King Abdullah also assured Bush in a telephone conversation of the "support of the kingdom to its friend the United States during its misfortune."

King Abdullah said the kingdom, the world's top oil exporter, was prepared to "do everything that it can to help towards lessening the consequences of the hurricane."

Italian Prime Minister Silvio Berlusconi sent a brief message of condolence and support to Bush.

"Dear George, I am with you and the American people in this moment of distress," read the message released by Berlusconi's office.

Sympathy also came from the head of the Greek Orthodox Church in a message to Bush as well as from Greece's prime minister.

"Our thoughts go out to the relatives of the victims and to all those who are suffering the consequences of this catastrophe," said the Greek leader, Costas Karamanlis.

As rescuers search for survivors and officials begin to assess the massive property damage from the fierce hurricane, the Chinese government hailed the resilience of the American people.

"The American people will overcome the aftermath of the disaster and rebuild their homeland," Chinese President Hu Jintao said in a message.

Hu is set to hold talks with Bush in Washington next Wednesday on his first visit to the US as China's head of state.

The OPEC oil cartel also sent a message of condolence to the US government and people, vowing to do its utmost to ensure the stability of the global oil market in the wake of Hurricane Katrina.

"Our deepest sympathy goes out to the families and friends of all those who lost their lives or who have been injured in this natural catastrophe of unimaginable dimensions," the organisation said.

All rights reserved. � 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.