(CNN) Hong Kong pro-democracy activist leader Joshua Wong has appealed to the German Chancellor Angela Merkel for help ahead of her upcoming visit to China.

The open letter -- from the "Hongkongers in Germany Concern Group," the "Civil Human Rights Front," and activists Joephy Wong Sze-ting, Wong, and Alice Yu Ka-hei -- calls on Merkel "to express concern over our dire situation and put forward our demands to the Chinese government during your stay.''

On Thursday, Merkel will land in China for a three-day trip, accompanied by a large business delegation.

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Drawing on Merkel's decades living in communist East Germany, the letter reads: "Chancellor Merkel, you grew up in the GDR [German Democratic Republic]. You have first-hand experience of the terrors of a dictatorial government."

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