North Korea’s nuclear test last month rattled South Korea so much that some politicians are calling it an inflection point, with some now arguing openly that Seoul should develop nuclear weapons.

South Korean Foreign Minister Yun Byung-se told foreign officials that the North’s nuclear test last month, its second of the year and most powerful yet, is being viewed by many in his country as “a kind of Sept. 11 attack,” the Yonhap news agency reported Sunday, citing official sources. The Sept. 11, 2001, terrorist attacks on the U.S. defined security concerns there for a generation.

Yun “has been comparing the Sept. 9 test to the al-Qaida attack in recent meetings with foreign officials,” a diplomatic source was quoted as saying. The source, who declined to be identified, said the purpose of linking the two events was to drive home the view in the South that “circumstances are extremely grave” in the wake of the North’s nuclear and missile tests.

Pyongyang has also conducted a spate of ballistic missile tests this year, including one fired from a submarine in August that flew 500 km over the Sea of Japan.

“Just as the United States’ perception of terrorism changed after the Sept. 11 attacks, the foreign minister is pointing out that the North’s nuclear capability must be viewed differently compared with the past,” the source added. “This is especially true since Pyongyang has threatened pre-emptive strikes.”

The report cited the source as saying that Yun’s remarks highlighted the need for “drastic changes” in the way the world approaches North Korea.

It also comes after Yun met the top diplomats from 40 other countries on the sidelines of the United Nations General Assembly last month in an effort to drum up support for applying fresh pressure on the isolated nation.

Washington and Seoul are working closely to develop more effective ways of reining in Pyongyang, officials say. However, unease has been growing in the South over the U.S. response to the latest test, as well as its commitment to protecting the country.

There have even been calls from leading lawmakers in the South for the return of U.S. nuclear weapons to the peninsula or for Seoul to develop its own atomic arsenal.

In a separate interview Sunday with Yonhap, Gyeonggi provincial Gov. Nam Kyung-pil, who is believed to be weighing a presidential bid with the ruling Saenuri Party, said the country should prepare to arm itself with nuclear weapons.

Nam cited concerns over the U.S. potentially withdrawing its nuclear umbrella.

“It’s time for us to consider various options, and one of them is to prepare for nuclear armament,” he was quoted as saying. “Preparations for nuclear armament should begin with the next government, or, in fact, now.”

Republican U.S. presidential nominee Donald Trump has threatened to pull American troops out of South Korea and Japan if elected president, unless Seoul and Tokyo pay more for their presence.

Trump has also suggested that the two Asian neighbors should have their own nuclear arsenals to make them less dependent on the U.S. for protection.

Calls have also grown in the U.S. for Washington to hold direct talks with Pyongyang to negotiate a freeze on the communist nation’s nuclear and missile programs first before seeking to dismantle them.