North Korea's Minister of Public Security Ri Myong-su met with his Chinese counterpart Meng Jianzhu in Beijing on Thursday, the North's official KCNA news agency reported.
It was the first time in three years and eight months that a North Korean minister of public security has visited China since the Ri's predecessor Ju Sang-song.
A government source here said Ju's visit at the time "was mostly to negotiate security and bodyguard issues prior to [then-leader] Kim Jong-il's visit in May the following year, so we're trying to find out whether that means [new leader] Kim Jong-un is going to visit China soon."
Others speculate that Ri's visit may be linked to the release of Kim Young-hwan, a prominent South Korean activist who has been helping North Korean defectors. Kim was jailed in China for over 100 days charged with endangering national security.
An intelligence officer said, "North Korea is unhappy with China's decision to let Kim Young-hwan go." He added border controls between North Korea and China have historically been toughened after every meeting between security ministers of both countries. "This may make escape from North Korea difficult for quite some time," he said.