Beijing (CNN) -- Prominent human rights activist Hu Jia, who was released over the weekend after serving a 3 1/2-year sentence, is promising his parents he will be "careful" in the future.
In a phone call to CNN affiliate iCable News in Hong Kong on Sunday, Hu said his parents had asked him to not clash with the system.
"Once I saw my family, I understood how much I owe them, especially my parents, my wife and my kid. I realize I've done nothing for them. There is a Chinese saying that 'patriotism and filial piety don't go hand in hand,'" he said in the phone call.
"They told me to be a good citizen and don't clash with the system. This system is very brutal. It uses government's power to violate people's dignity. I can only tell my parents, I will be careful."
Chinese authorities released Hu on Sunday, days after freeing renowned dissident artist Ai Weiwei.
Hu, 37, denounced China's human rights record in a series of articles ahead of the 2008 Beijing Olympics and was later sentenced to 3.5 years in prison for "inciting to subvert state power."
He also has been active on AIDS issues in China.
Ai, the conceptual artist turned government critic, was released Wednesday on bail after authorities detained him for nearly three months for tax evasion, the state-run Xinhua news agency reported.
On Sunday, police guarded entrances to Hu's apartment compound and patrolled surrounding streets. Zeng Jinyan, his wife, appeared unreachable via phone or the Internet.
Zeng told CNN Friday that authorities started 24-hour surveillance on her several days before Hu's expected return. In an interview last December, she predicted a virtual prisoner's life for the couple in their housing complex, called Freedom City.
"Hu Jia told me that he won't change, and police told him they may put him under house arrest in that case," she said. "I'm prepared for it."
"As long as there's no democracy or the rule of law in China, our situation won't change at all."
Last year's Nobel peace laureate Liu Xiaobo, also a rights activist, was convicted of the same crime as Hu. Liu is still serving an 11-year jail term.
Activists say the Chinese government, worried about potential uprisings inspired by the Arab Spring, has been increasingly tightening its grip on freedom of expression, targeting not only political dissidents but also intellectuals and artists.
In his phone call to iCable, Hu talked further about his parents and his responsibility toward them and others like them.
"My parents are very old. How many parents are like my parents? Others, too, are also in pain but not getting as much attention and help from you all as I did," he said. "These people are more isolated. I can only try my best to comfort my parents and comfort the others too."