North Korea is a major threat to the country most people think is its friend: China

China should be more worried than the U.S. about this week's murder of Kim Jong Un's half brother Kim Jong Nam and a missile test, some analysts say.

"China must do something otherwise they no longer look like a serious power," said Bruce Bennett, senior defense analyst at research organization Rand Corp.

"These two particular cases" — the assassination and the launch — "look like they're really against Chinese interests," he said. "The U.S. needs to really sit down with China and say look, this was as much against you as it was against us."

Last weekend, North Korea test launched a missile from a region near its border with China called Panghyon, Reuters reported, citing South Korea's Office of the Joint Chief of Staff. The missile flew about 500 km (300 miles) into the Sea of Japan, the report said.

Potential range of missile from Panghyon, North Korea

Geng Shuang, China's foreign ministry spokesman, said in news briefings this week that China opposes North Korean missile tests which violate UN Security Council resolutions and is monitoring developments following the death of Kim Jong Nam in Malaysia. The two countries have "a tradition of friendly exchanges," Shuang said.

However, newswire service United Press International reported Wednesday, citing Hong Kong's Oriental Daily News and the nongovernmental Information Center for Human Rights and Democracy, that Beijing has deployed 1,000 additional soldiers to the North Korean border.

Beijing has not issued a statement on the military move, the newswire said, although locals confirmed the troops' arrival to the Hong Kong newspaper.

From the Chinese perspective, North Korea has long served as buffer between itself and U.S. ally South Korea, where almost 30,000 American soldiers are stationed. There are another 49,000 U.S. troops in Japan.

"The reason China has a lot more to fear is that North Korea could collapse." -Isaac Stone Fish, senior fellow, Asia Society's Center on U.S.-China Relations

An estimated two-thirds or more of North Korea's trade is with China, and the U.S. has repeatedly but ineffectively pressured Beijing to curb North Korea's missile tests.

"The reason China has a lot more to fear is that North Korea could collapse," Isaac Stone Fish, senior fellow at Asia Society's Center on U.S.-China Relations.

He pointed out that a failed state would likely result in hundreds of thousands of refugees going into China's economically weak northeast region, while the collapse of North Korea would also likely strengthen the presence of U.S. ally South Korea on the peninsula.

Presumably, a unified Korea would look a lot more like U.S. ally South Korea than like isolated pariah state North Korea.

Meanwhile, North Korean dictator Kim Jong Un appears to have further asserted his control following this week's assassination of his half brother Kim Jong Nam.

Many international observers believe that Kim Jong Nam was under the protection of China as potential leverage against the rogue state's dictator.

"That side of the family seemed to have more of China's interests in mind than Kim Jong Un," Fish said.

Nam was killed in Malaysia, and to some observers, his travel outside of China provided the opportunity for assassination. Malaysian officials have not confirmed North Korea was behind the murder.

"It's hard to draw a conclusion other than simply saying worries now are stronger than they were a week ago," said Donald Straszheim, head of China research at Evercore ISI.