The note, which was 15th such communication in less than three months, specifically mentioned tailing of the vehicles of India's deputy high commissioner, military attache, air attache and naval attache on Tuesday.
The vehicles were aggressively tailed on motorcycles in close proximity within a threatening distance, while coming from residence to Chancery and going back from Chancery to residence, they said.
The sources said staff members of the high commission received unsolicited and objectionable calls from Pakistan registered numbers on their phones five-six times since Monday.
They said another diplomat of the mission, who was going to Australian High Commission for a meeting, was aggressively followed by two people in a Mehran Suzuki car.
"We have requested Pakistan to immediately investigate all these incidents and direct the relevant authorities to ensure that such incidents do not recur. Results of the investigations may kindly be shared with the High Commission," said a source.
The note verbale was sent today to Pakistan Foreign Ministry by the High Commission.
The sources said the website of the High Commission of India continues to be intermittently blocked and it is causing inconvenience and has affected normal functioning of the mission.
They said such incidents of harassment, intimidation and threats to physical security of diplomats and officials are in violation of the Vienna Convention on Diplomatic Relations of 1961, and a threat to the security and safety of the personnel of the High Commission of India.
Pakistan has also been accusing India of harassing its diplomats and releasing videos of alleged intimidation of its officials. However, the veracity of these videos could not be ascertained.
Islamabad has also called its High Commissioner to India back home for consultations on the issue.
Bajwa wants India-Pak talks. Can he be trusted?
Why India must worry about the Pakistan threat
We are close to war with Pakistan
Why a future war with Pakistan is certain
Can India fight China and Pakistan simultaneously?