The Sikkim section of the China-India border was officially defined by the Convention Between Great Britain and China Relating to Sikkim and Tibet in 1890, and the Indian government has repeatedly confirmed in written forms that there is no objection, Chinese Ministry of Foreign Affairs spokesperson Geng Shuang said at a regular press conference in Beijing on Wednesday.

Geng's reiteration came after India's Foreign Secretary S. Jaishankar Tuesday commented on the rising tensions between Indian and Chinese troops in the Donglang area of the Sikkim section of the China-India border.

"It is a long border," Jaishankar told media in Singapore. "As you know, no part of the border has been agreed upon. It is likely that from time to time there are differences."

However, Geng said that Indian border troops have crossed the China-India boundary at the Sikkim section and entered Chinese territory, which is "essentially different from previous conflicts in some other undefined areas."

"The origin of the Sikkim section of the China-India border has special historical background, and it is the only boundary line mutually defined and confirmed by two sides in the Convention in 1890," Geng said, urging India to respect China's territorial sovereignty and immediately withdraw troops to its own side of the border.

Earlier in June, Geng confirmed the border incursion, saying Indian border guards "obstructed normal activities" of Chinese frontier forces, adding China took counter-measures and thoroughly investigated the matter.