Islamabad: Pakistan's National Security Committee (NSC) decided the country would issue a strong demarche to an unnamed country whose official communicated the "threat" to the south Asian country, media reports said on Thursday.

"The Committee decided that Pakistan will issue a strong demarche to the country in question both in Islamabad and in the country's capital through proper channel in keeping with diplomatic norms," a statement issued from the Pakistan Prime Minister's Office said.

The NSC meeting was chaired by Imran Khan.

During the meeting, Pakistan National Security Adviser Moeed Yusuf briefed the committee on the formal communication of a senior official of a foreign country to Pakistan's ambassador in the said country in a formal meeting, Geo News reported.

According to the statement, the Pakistani ambassador "duly conveyed" the message of the foreign official to the country's Ministry of Foreign Affairs.

The NSC expressed concern at the communication, terming the language used by the foreign official as undiplomatic.

The communication reportedly amounted to blatant interference in the internal affairs of Pakistan by the country in question, which was unacceptable under any circumstances, the report said.

Pakistan PM earlier shared the contents of a secret letter that was in news last week when he informed a public meeting that his government had received threats from abroad.

Imran Khan had claimed that the threatening letter had been sent to the Ministry of Foreign Affairs.

Pakistan media reports said that letter is the word-for-word transcript of a conversation between the diplomats of Pakistan and another country sent to Pakistan's Foreign Ministry.