Chinese President Hu delivers speech during opening ceremony of 18th National Congress of the Communist Party of China in Beijing.

Chinese President Hu Jintao has officially opened the 18th National Congress of the Communist Party of China in Beijing by reminding delegates of the risks and challenges the nation faces while it treads the path of development.

In a 90-minute speech opening the week-long session, Hu said China was facing "unprecedented challenges and opportunities". He also talked about amending the political structure and adopting a more sensible approach to democracy.

"Reform of the political structure is an important part of China's overall reform. We must continue to make both active and prudent efforts to carry out the reform of the political structure and make people's democracy more extensive, fuller in scope and sounder in practice," said Hu in his speech.

"At present, as the global, national and our party's conditions continue to undergo profound changes, we are faced with unprecedented opportunities for development as well as risks and challenges unknown before.

"We must never let words act in place of the law or [personal] power replaces the law; nor will we allow the ignoring of the law for personal benefit."

Over 2,000 party-picked delegates are in attendance at the Great Hall of the People for the party congress which will witness the once-in-a-decade leadership change.

The week-long congress will see Vice President Xi Jinping, the anointed successor to Hu, taking over as the party chief. He will officially take over his state duties as China's president at the annual meeting of parliament in March.

Seven of the present nine-member standing committee will step down during the congress, leaving Xi and Li Keqiang who is expected to become the deputy party leader.

The party congress is taking place at a time when China's top political leadership is facing allegations of corruption of an unprecedented magnitude. Allegations include accumulation of personal wealth, abuse of office, bribery and crime.

The party has expelled one of its senior regional leaders, Bo Xilai, ahead of the congress accusing him of abuse of office, bribe-taking as well as crime.

A recent New York Times report elaborated how close relatives of Chinese Premier Wen Jiabao amassed wealth to the tune of at least $2.7bn (£1.67bn) forcing the government to block the NYT websites in China.

Security has been tightened in and around the Great Hall where the congress is taking place and the nearby Tiananmen Square, scene of the 1989 pro-democracy protest. Authorities are keeping a close vigil on activists and have clamped down heavily on dissidents, putting many of them under house arrest.

"My internet has been cut off, I can't receive telephone calls and three people follow me when I leave the house to walk my dog," Xinna, the wife of one of China's longest-serving political prisoners, Mongol rights activist Hada, told Reuters.