Leaders of China and the Philippines have expressed deep sorrow over the hostage crisis that ended in the deaths of eight tourists from China's Hong Kong, while a working team sent by the Chinese government has arrived in Manila to deal with the aftermath.

Chinese President Hu Jintao and Premier Wen Jiabao on Tuesday expressed their condolences to the families of the eight Hong Kong tourists killed during Monday's hostage crisis in the Philippines.

In a joint letter to Donald Tsang Yam-kuen, chief executive of Hong Kong Special Administrative Region (SAR), Hu and Wen expressed their deep sorrow for the families of those killed and consolation for the injured.

"We are in grave shock and grief on hearing that eight Hong Kong compatriots fell and many others were injured in the Manila hostage incident," the letter said.

"We hereby express our grave condolences and our deep sympathy to the families of the Hong Kong compatriots, and we hope the injured will recover soon," the letter said.

Chinese Vice President Xi Jinping on Tuesday also expressed his condolence in a letter to Tsang.

Philippine President Benigno Aquino III has declared Aug. 25 a day of national mourning for the victims of the hostage crisis.

Presidential Spokesman Edwin Lacierda said Tuesday that Aquino has ordered all government agencies, including the country's embassies and consulates abroad, to lower the Philippine flag at half-mast.

The eleven-hour hostage crisis in the Philippine capital Manila ended with the death of eight tourists from Hong Kong. Thirteen other Hong Kong tourists survived the ordeal, seven of them injured.

The hijacker, former Police Senior Inspector Rolando Mendoza, was killed after police raided the bus following failed negotiations to save the hostages.

The Chinese government has strongly condemned the hostage crisis and demanded the Philippine government thoroughly investigate the incident.

Foreign Minister Yang Jiechi, during a telephone conversation with his Philippine counterpart Alberto Romulo, said the Chinese government was shocked about the incident, deplored the slaying of the Hong Kong tourists, and strongly condemned brutality against innocent tourists.

The Chinese government demands the Philippine government launch a thorough investigation into the incident and inform the Chinese side of related details as soon as possible, he said.

Meanwhile, a working team sent by the Chinese government to deal with the hostage crisis arrived in Manila on Tuesday morning, accompanied by Chinese Ambassador to the Philippines Liu Jianchao, who had terminated his work report in Beijing ahead of schedule.

The Chinese governmental working team, headed by Guo Shaochun, a consul of China's Foreign Ministry, was greeted by Philippine Vice-President Jejomar Binay, Executive Secretary Paquito Ochoa Jr. and Romulo, and the two parties held a talk.

Liu said China hopes that the Philippines will inform China about the result of the investigation as soon as possible and that the Philippines will protect foreign tourists well in the future, including those from China, and avoid similar tragedies.

Binay conveyed condolences over the killed hostages on behalf of the Philippine government, saying that the Philippines will closely cooperate with China on this issue, provide all necessary assistance and deal with the aftermath appropriately.

Romulo said that after the incident, he called Chinese Foreign Minister Yang at the request of Aquino, telling his Chinese counterpart that the Philippines is conducting an overall and serious investigation into the incident.

Once the investigation report is completed, Romulo said, he will go to Beijing to submit the report.

Later on Tuesday when meeting with Liu, Aquino said that Binay and Romulo will go to Beijing to submit a report on the hostage incident after the investigation is over.

Liu and members of the working team visited the hospital to convey condolences of the Chinese leaders to the injured, saying the Chinese government is ready to provide all necessary help.

A chartered plane carrying officials from the Hong Kong government and the family members of those who died in the hostage crisis also arrived in Manila Tuesday morning to bring back the bodies of the victims and to comfort the survivors.

Meanwhile in Hong Kong, all the city's government offices flew their flags at half-mast to mourn the hostage victims on Tuesday.

The city government said that the Hong Kong SAR flags at all government offices would continue to be flown at half-mast on Wednesday and Thursday as a token of mourning for victims of the hostage incident.

China's National Tourism Administration had reminded Chinese nationals to exercise caution in visiting the Philippines, saying those who are currently in the country must pay attention to security risks.