The police are investigating an email threatening to blow up Seoul City Hall on this week’s Liberation Day, officials said Monday.

According to police, the email stated that high-powered bombs were installed in several locations around Seoul City Hall, with detonation set for 3:34 p.m. Tuesday. The email, sent from a Japanese account to local media outlets, was received Sunday afternoon.

The email, sent in English, Japanese and Korean, stated, "There are bombs planted in several places around Seoul City Hall. In particular, bombs have been planted in restrooms, so you'll have to search carefully."

The police are in the process of tracking down the sender. They have noted that the bomb threat was sent in a similar manner to the message sent on Aug. 7 and Aug. 9 targeting the Democratic Party of Korea’s leader Lee Jae-myung.

On Aug. 7, Seoul’s city government officials received an email threatening to blow up an explosive in Seoul if Lee was not killed. Two days later, another email threatening to blow up the National Museum of Korea, Embassy of Japan in Korea, N Seoul Tower and the Japanese School in Seoul was reported to the police.

Like previous emails, the latest was sent in the name of Takahiro Karasawa, a Japanese lawyer, and included his contact information and law firm's address. Earlier emails were also sent under the name of a Japanese law firm and Japan's Ministry of Internal Affairs and Communications.

In Japan, there has been a recent increase in phishing attack emails sent from accounts belonging to lawyers and law firms.

The police have asked the Tokyo Metropolitan Police Department’s for cooperation to identify the suspects behind the crime.