Police confirmed on Tuesday that the estranged half-brother of North Korean leader Kim Jong Un was killed in Malaysia, apparently assassinated by two women, according to reports.

Kim Jong Nam, the older half-brother of the North Korean leader, was known to spend a significant amount of his time outside the country and had spoken out publicly against his family's dynastic control of the isolated state.

"It's another sign that Kim Jong Un is asserting his control over the regime — rather than the regime descending into chaos," said Anwita Basu, lead analyst for North Korea at the Economist Intelligence Unit, in London. "He was a threat and he was removed."

Several media reports in South Korea and elsewhere indicated that the female assassins, who are believed to be North Korean agents, attacked Kim Jong Nam at Kulala Lumpur airport with "poisoned needles." The pair escaped from the scene and are at large.

Also read: eBay founder is testing giving people free money

The apparent murder comes as tensions are rising following another North Korean missile launch, on Sunday . The isolated country is armed with nuclear weapons and has developed increasingly sophisticated missile technology — and at a faster pace than in previous years. Observers fear those weapons could be used to threaten Japan or South Korea , two critical U.S. allies and two of the world's biggest economies.

Nikki Haley, the U.S. ambassador to the United Nations, on Monday issued a statement to the Security Council saying it's "time to hold North Korea accountable, not with our words, but with our actions." Her statement made pointed reference to North Korea's "enablers," an apparent reference to China , which is the only country in the world with any meaningful relations with North Korea.

The United States has a long history of leaning on China to rein in North Korea, but that strategy has never worked at slowing North Korea's weapons development.

Also read: Treasurer threatens tax hike to fund NDIS

"With the nuclear program, that's one of those things that I feel almost is fueling the economy. A lot of North Korean revenues come from its arms dealings and its prowess as an arms technologist," said Basu. "We haven't seen any evidence of the nuclear program becoming less developed under further sanctions."

Kim family has a history of murderous rivalries

Kim Jong Nam was believed to be close to his uncle, Jang Song Thaek, whom Kim Jong Un ordered killed in 2013 shortly after he took control of the ultra-authoritarian state.

Kim Jong Nam and Kim Jong Un are both sons of former leader Kim Jong Il, who died in late 2011, but they had different mothers.

In 2001, Kim Jong Nam was caught at an airport in Japan traveling on a fake passport. He explained at the time that he wanted to take his family to Tokyo Disneyland. That embarrassing incident is widely believed to have been the reason that his father Kim Jong Il decided against him and in favor of his younger son, Kim Jong Un, as his heir.

Kim Jong Nam said several times over the years that he had no interest in leading his country.

"Personally I am against third-generation succession," he told Japan's Asahi TV in 2010, before his younger had succeeded their father. "I hope my younger brother will do his best for the sake of North Koreans' prosperous lives."

The South Korean government source who spoke to Reuters did not immediately provide further details.

South Korea's foreign ministry said it could not confirm the reports, and the country's intelligence agency could not immediately be reached for comment.

—CNBC's Evelyn Cheng and Reuters contributed to this report.