New Delhi, May 12: India has protested Chinese President Xi Jinping's commitment to investments in Pakistan-occupied Kashmir last month, the foreign office revealed today, 36 hours before Prime Minister Narendra Modi flies to China on a trip that represents his most challenging yet in office.

Foreign secretary Subrahmanyam Jaishankar summoned Chinese ambassador Le Yucheng to the ministry of external affairs headquarters to convey India's unhappiness over Xi's promise, a day after the Chinese President returned to Beijing from Islamabad, senior officials confirmed today.

Indian ambassador in Beijing, Ashok Kantha, also drove down to China's ministry of foreign affairs to deliver a demarche - a formal, written protest - Jaishankar said this evening. New Delhi has argued that Chinese investments in PoK legitimize Pakistan's occupation of Indian territory.

"We have taken up this matter with the Chinese," Jaishankar said, answering a question on India's response to Xi's promise, made in Islamabad during a trip timed less than a month before Modi's visit to China.

Modi lands in Xi'an, the closest city to Xi's hometown in China's Shaanxi province, on Thursday morning. After meeting Xi there - a reciprocal visit to the Chinese President's trip to Ahmedabad last September - the Indian Prime Minister will fly to Beijing on the night of May 14 and spend the next day in the Chinese capital. He will end his trip to China with a visit to Shanghai on May 16. From China, Modi flies to Mongolia and then South Korea.

China's presence in PoK is only one of many irritants in a relationship that has witnessed both a war in 1962 and over three decades of peace since the 1980s along a contested border than runs from Jammu and Kashmir to Arunachal Pradesh.

It is also not uncommon for India and China to issue demarches to each other to protest diplomatic moves either side sees as counterproductive to their relationship.

But the timing of the decision to reveal the Indian demarches suggests the confirmation of the protest today may not have been a coincidence, and may have been aimed at sending Beijing a public signal.

Every word, gesture and act ahead of a bilateral meeting with China's leaders is usually carefully measured and thought through, because of Beijing's traditional sensitivity that almost borders on prickliness.

The foreign office could have revealed the demarches when they were delivered - almost three weeks back - to allow the tension to dissipate by the time the PM travels to China. It could alternatively have continued to stay mum in response to questions on India's response to Xi's promise, as it has till now.

Instead, Jaishankar chose to reveal the demarches just before Modi flies to China, and on a day a major Chinese state-run newspaper published a commentary mocking the Indian Prime Minister.

The opinion piece by Shanghai Academy of Social Sciences research fellow Hu Zhiyong, published in the Global Times, argues that "Modi has been busy strengthening India's ties with neighbouring countries to compete with China."

"Modi has also been playing little tricks over border disputes and security issues, hoping to boost his domestic prestige while increasing his leverage in negotiations with China," Hu wrote, citing the "Indian elites' blind arrogance and confidence in their democracy" as a stumbling block for ties.

The Indian Prime Minister, the article argues, "should no longer visit the disputed region (Arunachal Pradesh) in pursuit of his own political interests."

India has, however, countered by arguing that the Prime Minister and any government official is free to travel to Arunachal Pradesh any time - as it belongs to India. Defence minister Manohar Parrikar is also visiting the north-eastern state, his trip also timed on the eve of Modi's departure for China.