China reacted cautiously to North Korea's latest nuclear test, despite apparently making last-minute efforts behind the scenes to stop it.

Chinese Foreign Minister Yang Jiechi summoned North Korean ambassador to Beijing Ji Jae-ryong on Tuesday to lodge a formal protest and discussed a response on the phone with U.S. Secretary of State John Kerry and South Korean Foreign Minister Kim Sung-hwan. But there was no forceful public condemnation from Beijing.

In his conversations with Kerry and Kim, Yang mostly called for "calm and restraint" from neighboring countries. And a letter of protest handed to the North Korean ambassador was merely a slight revision of a statement after the North's second nuclear test in 2009.

Beijing also opposed the inclusion of a clause in a UN Security Council statement denouncing the nuclear test that would have provided grounds for military action. The clause was then left out of the initial draft.

Guo Chongli, China's former ambassador to Kenya, said in a discussion hosted by a Hong Kong daily that Beijing's opposition to the nuclear test "does not mean China is against all of North Korea." Guo added that North Korea's "rise and fall has a profound effect on China's security interests."

A former Chinese ambassador to South Korea, stressed that the top priority for China is "stability on the Korean peninsula" followed by "friendship" with North Korea.

The quasi-official Global Times on Wednesday reported that China had tried its best to stop the nuclear test.