China's newly appointed leader Xi Jinping pledged Tuesday to implement rule of law, in comments that appeared aimed at rising social discontent over government corruption and police brutality.

In a speech at the Great Hall of the People that marked the 30th anniversary of China's 1982 constitution, Xi spoke of curbing the near-dictatorial powers of the ruling party.

His comments appeared to be the strongest yet by a Chinese leader on the need for legal restraints on the party and come amid a series of graft scandals and reports of the unbridled wealth of China's top communist families.

"We must firmly establish throughout society the authority of the constitution and the law and allow the overwhelming masses to fully believe in the law," Xi said in comments carried by China Central Television.

"To fully implement the constitution needs to be the sole task and the basic work in building a socialist nation ruled by law."

Xi was last month named as the head of the ruling Communist Party and is slated to take over the state presidency from current President Hu Jintao in March as part of China's once-a-decade leadership transition.

This year's transition was badly rocked by the case of disgraced politician Bo Xilai, whose wife was convicted in August of murdering a British businessman, in a scandal that has revealed rampant graft and lawlessness at the pinnacle of political power.

Bo is awaiting trial for corruption and abuse of power after allegedly using police in Chongqing city where he ruled to remove political opponents and dissidents, practices that are routine in China.

Since becoming party head, Xi has repeatedly pledged to fight graft and on Tuesday he further vowed to rein in China's top leaders.

"We must establish mechanisms to restrain and supervise power, power must be made responsible, power must be supervised, violations of law must be investigated," he said.

"We must ensure that the power bestowed by the people is constantly used for the interest of the people."

"No organisation or individual has the special rights to overstep the constitution and law, any violation of the constitution and the law must be investigated."

China's current constitution has enshrined the basic freedoms of speech, press, religious belief and association, but such rights are routinely sanctioned and violated, rights groups say.

Xi also appeared to address such alleged rights violations.

"To ensure the implementation of the constitution, is to ensure the realisation of the basic rights of the people," he said.

"By defending the dignity for the law, we are defending the will of the party and the people for dignity."