Beijing (CNN) Li Peng, the former Chinese Premier remembered for his role in the brutal military suppression of the 1989 Tiananmen Square protesters, has died aged 91, according to state-run media.

Li died of an unspecified illness in Beijing on Monday night, the state-run Xinhua news agency reported Tuesday. State media listed him as 91 using the Chinese method of counting age. He would have been 90 in the Western calendar.

During the pro-democracy movement that swept China in the spring of 1989, Li was the face of hardline leaders who refused to negotiate with the protesters and sided with then-paramount leader Deng Xiaoping in ordering the military crackdown.

It was Li who, as Premier, declared martial law in Beijing on national television on May 20, 1989, paving the way for the Tiananmen Square massacre two weeks later, in which hundreds of people were killed.

Some of the 200,000 pro-democracy student protesters sit face to face with policemen outside the Great Hall of the People in Tiananmen Square on April 22, 1989.

Despite his controversial image, Li remained unchallenged as China's number two leader through the 1990s and into the early 2000s, second only to then-President Jiang Zemin, as the ruling Communist Party tried to present a united front.

His preference for state control over market forces in running the economy, however, reportedly led to him losing influence as Premier to his lieutenant Zhu Rongji, handpicked by Deng to resurrect stalled economic reforms and market liberalization.

After Li suffered a heart attack in 1993, Zhu gradually assumed more responsibility for the country's economic policies and eventually succeeded Li as Premier in 1998. Li retained his second-highest rank within the party hierarchy, however, moving to the National People's Congress, China's rubber-stamp parliament, and presiding over the legislature until his retirement in 2003.

Chinese President Jiang Zemin (L) chats with Chairman of the National People's Congress Li Peng during the opening session of the Chinese People's Political Consultative Committee in Beijing in 2002.

Li was born in 1928 in Shanghai, to a Communist "martyr" father who was executed by the then-ruling Nationalist government. He was widely said to have been adopted by Zhou Enlai, Communist China's highly respected first Premier who occupied the post from 1949 until his death in 1976.

Having joined the Party as a teenager, he went on to study and graduate from the Moscow Power Engineering Institute while serving as president of the Chinese student association in the Soviet Union. Trained as a hydroelectric engineer, Li worked in China's power industry upon his return in 1955 -- and steadily climbed through the Party's ranks.

Li survived Chairman Mao's tumultuous Cultural Revolution largely unscathed, thanks to his connection to then-Premier Zhou. After Deng became China's top ruler in the late 1970s, Li's political fortune continued to rise, despite clashes between his conservative ideology and the reformist agenda of a more liberal Party leadership wing. He headed several ministries in the 1980s and eventually became Premier in 1988.

In the memoirs of former Communist Party General Secretary Zhao Ziyang, who led China from 1987 to 1989, Li was portrayed as the leader of the Party faction that opposed economic reforms and supported greater state control across the country. Zhao was deposed in 1989 for objecting to a military crackdown on the Tiananmen Square protesters.

Li kept a relatively low profile after retiring in 2003, though his family's tight grip on the country's energy sector -- thanks to his background and former positions -- attracted continued attention and allegations of corruption. His close association with the controversial Three Gorges Dam, a multibillion-dollar hydroelectric project he personally oversaw, was another point of contention in his legacy.

Li was last seen in public in October 2017 during the 19th Communist Party Congress as current President Xi Jinping further consolidated power while former leaders' influence waned.

In a 2010 autobiography titled "The Critical Moment," believed to be on based on his diaries, Li seemed to try to distance himself from the military crackdown in 1989, with critics seeing an attempt by him to shift most blame to Deng.