South Korea’s two largest political parties have decided to bolster security measures for their respective leader candidates, as both party conventions are scheduled to be held by the end of next month, sources close to the matter said Monday.

The moves follow the assassination attempt on former President Donald Trump in Pennsylvania, the US, last week, prompting concerns about political violence here as well.

With only a few weeks left until its July 23 party convention, the ruling People Power Party has decided to bolster security for its leadership candidates, a source close to the matter told The Korea Herald on Monday.

“We have decided to provide stronger security for our four candidates,” the source said.

Police on Monday afternoon launched an investigation into an online death threat made against former Justice Minister and ex-interim leader of the People Power Party Han Dong-hoon, who is one of the four candidates for the next ruling party leader. The Chungbuk Provincial Police said that they are currently tracking down the suspect who uploaded a post reading, "Stay down -- I'm going to carry eggs and a knife for revenge," to the forum of online used car platform Bobae Dream at 10:50 a.m. Officials also decided to bolster security for Han by dispatching police around his residence.

A source within the main opposition Democratic Party of Korea, which is also inching closer to its convention scheduled for next month, also said it is “doing everything” to protect the security of its candidates.

The upcoming election is expected to be a two-way race between former chair Rep. Lee Jae-myung and former South Gyeongsang Province Gov. Kim Doo-kwan.

The official said that the party is focused on preventing any additional attack on Lee, who himself suffered an assassination attempt while answering reporter questions in Busan on Jan. 2. A 67-year-old man posing as a supporter stabbed him in the neck, resulting in substantial damage to his jugular vein, requiring major surgery and over a week of hospitalization. The assailant was sentenced to 15 years in prison by a Busan court earlier this month.

Lee last Wednesday officially declared his bid for a second term as the party leader in the upcoming intra-party elections.

Attacks on politicians in Korea have occurred from time to time, with two major attacks having happened this year leading up to the April 10 general election.

A few weeks after Lee was attacked, People Power Party Rep. Bae Hyun-jin sustained a head injury after being repeatedly hit in the head with a brick by a teen assailant.

In 2015, the then-US ambassador to South Korea, Mark Lippert, was slashed in the face with a razor by a 55-year-old extreme nationalist named Kim Ki-jong before he was to give a speech at a function in Seoul. Lippert took 80 stitches to his face and hand. Lippert's assailant was sentenced to 12 years in prison.

Former President Park Geun-hye was injured in a knife attack in 2006 when she was the leader of the conservative Grand National Party, a predecessor of the current People Power Party. It left an 11-cm cut from her ear to her lower chin. She was campaigning for her party’s Seoul city mayoral candidate, Oh Se-hoon, at the time.