Japanese Prime Minister Shinzo Abe has said North Korea may be capable of arming missiles with the chemical weapon sarin, the same nerve agent used against Syrian civilians last week, Reuters reports.

Speaking to a session of parliament, Abe said “There is a possibility that North Korea already has a capability to deliver missiles with sarin as warheads.” His comments come at a time of increasing concern over a potential sixth North Korean nuclear weapons test, and heightening military tensions between South Korea, Japan, the United States, and North Korea.

Japan was itself the victim of a sarin gas attack in 1995, when a domestic terrorist cult organization called Aum Shinrikyo released sarin into the Tokyo subway system, killing 12 people and making thousands sick. The same group had used sarin the year prior in another attack, killing 8.

Abe provided no specific evidence that the North Koreans possessed the capability or intended to launch a chemical weapons attack on Japan, but North Korea is widely known to possess stocks of chemical weapons. It never signed the Chemical Weapons Convention, and experts believe they possess up to 5,000 tons of chemical weapons.

Abe’s political party has made efforts to expand the military capabilities of the Japanese military, known as the Japan Self-Defense Forces. Due to constitutional restrictions, their military is restricted from maintaining ‘offensive’ military units. However, with near routine North Korean nuclear tests, and missiles fired towards Japan and into the sea occurring regularly, many in Japan are seeking to expand their military options to confront the growing threat emanating from North Korea.

The Japanese otherwise rely heavily on the offensive and nuclear capabilities of the United States.

Sarin gas has been used intermittently since its creation as a weapon before World War Two. It was used a number of times by the Saddam-era Iraqi army against Iran during the Iran-Iraq war, as well as during the infamous Halabja attack that killed around 5,000 Kurds. Iraqi insurgents reportedly attempted to use sarin against a U.S. convoy in Iraq in 2004, to little effect.

Prime Minister Abe has historically taken a hard line against North Korea, and after series of ballistic missiles were fired towards Japan on March 6, said that “North Korea has entered a new stage of threat.”