Zhao is a revered figure among Chinese human rights defenders, in part for opposing the use of force to quell the 1989 Tiananmen Square democracy protests, when hundreds of unarmed civilians -- by some estimates, more than 1,000 -- were killed.

He was later deposed as premier and Communist Party general secretary, and forced to live under house arrest for the next 16 years until his death on January 17, 2005, aged 85.

Outside Zhao's former home in Beijing, where his ashes are kept along with those of his wife, groups of mourners were seen entering with baskets of flowers, watched by about a dozen security forces. Foreign journalists were prevented from entering.

Besides opposing Deng Xiaoping's imposition of martial law, Zhao was respected for carrying out economic reforms in the 1980s that created opportunities for many people.

Despite his contributions to China's economy, Zhao was not given a proper funeral as is generally afforded former leaders, and instead has been continually blamed for siding with the students.

Zhao's son-in-law Wang Zihua, in an interview with VOA, voiced the family's hopes that they would one day be able to give him a proper burial.

In an op-ed published earlier this week by US-funded Radio Free Asia, Bao Tong, an outspoken longtime aide to Zhao, condemned the authorities' practice of monitoring would-be mourners and deciding for themselves which of China's leaders were to be remembered.

"Of course, this is utterly ridiculous and makes a mockery of the rule of law," wrote Bao, who was purged along with Zhao and has spent much of the last 25 years either in jail, under house arrest, or facing other restrictions.

Zhao, he continued, "cared about ordinary people, so naturally they cared about him, too".

"He treated people like human beings, and he wanted everyone to become citizens in a commonwealth of the free," Bao wrote.

In an editorial, the state-run Global Times said silence from authorities "is also considered an official gesture".

"In the past 25 years, China has pursued a path that Zhao and his think tanks opposed at that time, becoming the world's second largest economy," the editorial stated. "China is using its actions and achievements to answer questions over the sensitive issues."

- Zhao's spirit is 'precious' -

Previous years have seen authorities prevent commemorations of Zhao's death.

"It has been many years since I have been able to go to Beijing to honour his memory," retired academic Sun Wenguang, who is kept under regular surveillance by Chinese authorities, told AFP by telephone.

Sun, at 81 one of China's oldest activists, was viciously beaten by authorities in 2009 when he sneaked past guards watching his building in an attempt to pay his respects on the anniversary of Zhao's death.

Zhao's spirit is "extremely precious", he said, adding it "deserves to be remembered and cherished".

In 2006, about 30 dissidents, petitioners and ordinary citizens planned to gather at the Beijing residence of activist Li Jinping a year after Zhao's demise.

But police placed at least a half-dozen of them under house arrest, including lawyer Gao Zhisheng and Qi Zhiyong, who lost his leg after troops shot him during the Tiananmen violence.

Li, who has a memorial to Zhao set up at his home, has been arrested multiple times since 2006 for trying to organise activities honouring the former leader.