Islamabad reportedly sent five engineers and staff employees working in Pakistan back to their home country of China for allegedly attacking police officers who denied them permission to leave their work camp to visit a “red-light” district.

The incident took place in Khanewal district in Pakistan’s Punjab province.

Neighboring China is Pakistan’s top economic and military ally in South Asia.

Referring to the incident that led to the removal of the Chinese immigrants, Pakistan’s Dawn newspaper notes that engineers and staff workers “clashed with security officials” on April 3 “for trying to stop them from leaving their camp without a security squad.”

Citing police officers, Dawn reports that the Chinese engineers and other officials wanted to leave their camp an visit a “red-light” area, ultimately resorting to violence when Pakistani police officers denied them permission to go out without being accompanied by security officials.

Dawn continues:

Several mobile phone clips doing rounds on social media showed Chinese nationals approaching the police officials in an aggressive manner and attacking them. A video showed a Chinese national standing on the bonnet of a police van, another video showed several Chinese nationals trashing policemen and some local people in plain clothes.

Although mainland Pakistan does not border China, the Muslim-majority Chinese province of Xinjiang shares an international boundary with Islamabad-occupied Kashmir.

China, Pakistan, and their rival India all have competing claims to the predominantly Muslim Himalayan region of Kashmir.

Dawn reports:

A letter, written by the Khanewal district administration to the Punjab government, had declared Xu Ling, Country Project Manager; Tian Weijun, Administration Officer; Liu Hui, Material and Equipment Manager; Wang Yifan, officer for Financial Affairs; and Tan Yang, Field Engineer, as “persona non grata being the reason of this incident”.

“They [Chinese workers] must have realized the sensitivity of their security and should not have taken the law in their hands,” the letter reportedly points out.

Despite the Islamic terrorism threat China faces from neighboring Pakistan, it continues to lend support to Islamabad. Amid tensions between the United States and Pakistan, Islamabad is growing even closer to China.

U.S. President Donald Trump’s administration has suspended an estimated $2 billion in security aid to Pakistan over its reluctance to combat terrorist group who use Pakistani soil to plan and carry out attacks against American troops and their allies.