Jerusalem, Apr 29 (IANS): The family of Israeli Prime Minister Naftali Bennett received a death threat letter with a live bullet in a mail, the second this week, the police said.

The police on Thursday said in a statement that an investigation was launched and their "Lahav 433" special unit and the internal security service Shin Bet are working in tandem on the case.

Israeli state-owned Kan TV news reported that the letter was addressed to Bennett's 17-year-old son Yoni.

The police did not say if any suspects have been arrested, Xinhua news agency reported.

The first letter and bullet were sent to the workplace of the Prime Minister's wife Gilat on Tuesday, which included threats against her and Yoni Bennett, said the police.

Following the first incident, the Shin Bet said the security around Bennett and his family has been increased.

The Israeli President said the threat was part of the heated political discourse in the country.

"Political conflict, no matter how deep, should not reach violence, thuggery and death threats," he wrote on Twitter, noting that "we must lower the flames of the political discourse."

It was not the first time Bennett and other leaders of the ruling coalition have received death threats, mainly by far-right activists, according to Kan TV.