Beijing (AFP) - President Xi Jinping urged China's youth on Tuesday to be loyal to the Communist Party as he sought to whip up patriotic sentiment in a nationalist speech marking the centennial of a student protest.

Xi delivered his hour-long plea at the Great Hall of the People to commemorate the May Fourth Movement, a landmark protest against colonialism and imperialism that rocked China in 1919.

The speech came as the party faces a slowing economy and a series of politically sensitive anniversaries, including 30 years since the June 4, 1989 crackdown on Tiananmen Square protesters.

"It's very shameful if a person isn't patriotic or even deceives or betrays the motherland. There is no place for such a person to stand anywhere," Xi told rows of young people, workers, soldiers and Communist Party cadres, many writing notes as he spoke.

"In contemporary China, the essence of patriotism is to combine one's love for the country with love for the party and socialism," he said.

"Chinese youth in the new era shall listen to the words of the party and follow the steps of the party."

The May 4, 1919 protest was a nationalist movement that began when some 3,000 Beijing University students marched to Tiananmen Square in anger at the handing of German concessions in China to Japan at the end of World War I.

The protests mushroomed into calls for a cultural and political awakening to modernise China.

Other sensitive dates loom this year, including the 30th anniversary of the Tiananmen protests, the 10th anniversary of riots in the restive Xinjiang region, and five years since the Hong Kong pro-democracy Umbrella Movement.

- Silencing campus activism -

While Xi has repeatedly extolled the teachings of Marx and the Communist Party, authorities have cracked down on Marxist students who backed labour movements in recent months.

Two sources close to a Marxist student group at elite Peking University told AFP Tuesday that they haven't been able to contact five students for over 24 hours, raising concerns that they may have been detained by police for taking part in an activity to mark Labour Day.

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The group includes Qiu Zhanxuan, the school's former Marxist society president, who was detained by police in December and later forced to step down by college administration after attempting to commemorate the 125th birthday of Mao Zedong, whose legacy in China remains controversial.

Qiu on Sunday posted online that he would work overnight with workers at an industrial park in Beijing to experience the life of manual labourers.

Plainclothes police had followed the students to the industrial park, a friend of Qiu told AFP.

"Chinese labour rights incidents happen one after another, and authorities are worried that progressive students will defend labour rights, which will affect the false 'harmony and stability' the government has created," said the student, who requested anonymity.

Beijing police and Peking University officials could not be reached for comment.

Considered China's most prestigious university, Peking has a history of student activism with its alumni playing a key role in the pro-democracy Tiananmen protests in 1989 and the May Fourth movement.

In his speech, Xi urged youth to "create a better life with hard work and honest labour."

"Youth should not be opportunistic and reject shortcuts," he warned.

Xi's speech was "ridiculously ironic," as the Communist Party was "using nationalism to suppress the rights of everyday people's struggles," the student said.