The mouthpiece of China's ruling Communist Party on Friday firmly rejected Western-style political reforms as reports emerged of detentions a day before a major party meeting.

The party "must uphold its leadership... in the face of some people in society who advocate imitation of the Western system," an article in the official People's Daily newspaper said.

The full-page article by the party's historical research institute defended China's former leader Mao Zedong, accusing those who attack his record of attempting to undermine the party.

A four-day plenum of around 380 top party members is set to begin on Saturday and is expected to announce some financial and economic reforms but no changes to China's authoritarian political system.

Important political meetings in China are generally preceded by a clampdown on political dissidents and "petitioners" -- people who travel to Beijing to file grievances with the government.

Rights groups and activists reported that several people had been detained in recent days.

Two petitioners travelling to Beijing ahead of the plenum were detained in a "black jail" -- a euphemism for illegal detention centres run by local governments, the advocacy group Chinese Human Rights Defenders said in a statement on Friday.

Prominent Chinese dissident Hu Jia told AFP that he had been placed under house arrest "due to the plenum". State security agents were stationed outside his door shortly after China's official Xinhua news agency reported the date of the plenum, he said.

The state-run Global Times, which has close links to the Communist party, played down desires for political changes among ordinary Chinese people.

It published a survey of about 1,300 urban residents, which showed that only 33 percent hoped for political reform, whereas around 80 percent favoured reforms to the welfare system.

However, as Chinese citizens risk reprisals for publicly expressing opposition to the Communist Party, some academics question the effectiveness of political polling in the country.

An online survey by liberal-leaning media company Caixin said that 63 percent of people believed "special interest groups," -- a phrase indicating those who benefit from the current system -- were the biggest obstacle to reform.

Just 29 percent of the around 1000 people surveyed said they were optimistic that the plenum would introduce major reforms, and most expected no changes in policy towards China's powerful state-owned enterprises, which have been blamed for stymieing market-oriented reforms.

Chinese officials have signalled that major reforms will be announced at the plenum, but analysts say that only broad economic policies are likely to emerge, partly due to opposition to change from within the party.