http://news.bbc.co.uk/2/hi/world/asia_pacific/10263325.stm
China says a North Korean border guard shot and killed three people near the countries' border last week.
A fourth person was reportedly injured in the incident near the north-eastern border town of Dandong.
China has made a formal complaint to North Korea, a spokesman for the Chinese foreign ministry said.
The two countries are considered to be close allies and Beijing rarely makes any public criticism of its isolated neighbour.
Foreign Ministry spokesman Qin Gang told a regular news conference in Beijing that the four residents of Dandong, in Liaoning province, had been shot "on suspicion of crossing the border for trade activities".
"China attaches great importance to that and has immediately raised a solemn representation with the DPRK," he said, using North Korea's full name (Democratic People's Republic of Korea).
Close ally
Mr Qin said the case was being investigated, but gave no further details. Pyongyang has not commented on the accusations.
Illegal traders regularly cross the border between North Korea and China, taking black market goods into the impoverished country.
China is North Korea's main trading partner and the country perceived to have the most influence on the state.
Map
Tensions on the Korean peninsula have been high since the sinking of a South Korean warship in March with the loss of 46 lives.
An international investigation blamed North Korea for the sinking, but China has resisted pressure to condemn its ally. Instead, it has urged both the Koreas to show restraint.
Last month, the North Korean leader, Kim Jong-il, was reported to have visited China to seek economic and political support.
China is crucial to North Korea's fight for economic survival, providing Pyongyang with food, fuel and much-needed investment.
Beijing is also a participant in the six-party talks on North Korea's nuclear programme. The talks have been going on since 2003 without much progress.
In 2009, North Korea detained two US journalists on the border with China, accusing them of entering North Korea illegally.
Laura Ling and Euna Lee, who said they were detained on the Chinese side, were sentenced to 12 years' hard labour but were freed in August after four months in captivity, as part of a diplomatic mission spearheaded by former US President Bill Clinton.
A US man, Robert Park, was also arrested in December last year, after walking into North Korea across a frozen river. He was released in February.
Super Drink
http://news.bbc.co.uk/2/hi/world/asia_pacific/10237314.stm
North Korea has developed a "super drink" that, it says, can multiply brain cells and stop skin ageing.
The secretive state's official news agency, KCNA, says the drink contains 60 kinds of "microelements" extracted from more than 30 species of plants.
It attracted "much interest from Chinese, German and other businessmen" at a trade fair in Pyongyang last month, the agency reports.
It was developed by a joint venture fruit juice company.
'No side-effect'
KCNA says: "It, with effects of both preventive and curative treatment, helps improve mental and retentive faculties by multiplying brain cells.
"It also protects skin from wrinkles and black spots and prevents such geriatric diseases as cerebral haemorrhage, myocardium and brain infarction by removing acid effete matters in time.
"It, much higher than quality cosmetics in anti-oxidation capacity, is efficacious for different skin diseases, including allergic dermatitis. It also makes skin fair.
"The drink has no side-effect."
The agency quotes a company manager, Jong Song Ho, as saying the drink has "proved efficacious among workers of such industrial establishments as thermal power station and smeltery and at medical institutions".
Nuclear Fusion
From Slashdot: "North Korea claims to have achieved nuclear fusion by building what it describes as a 'unique thermo-nuclear reaction device.' This announcement was met by skepticism on just about every news website this side of Saturn. Pyongyang claims its latest scientific breakthrough coincides with the birthday of the country's founder and eternal president Kim Il-sung. This is not the first time it seems that the laws of nature have been bent in his honor. According to official biographies, when his son, Kim Jong-il, was born, a new star appeared in the sky."
By John Sudworth
BBC News, Seoul
North Korean leader Kim Jong-Il (C) waving from a train while leaving Chinese capital of Beijing ending his five-day visit to China, May 2010
A new star appeared in the sky when Kim Jong-il was born, biographers say
North Korea has announced that it has made significant progress towards the development of thermo-nuclear power.
It is a claim that is likely to be met with some scepticism.
Despite hopes that the technology can produce large quantities of cheap, clean energy, no country has so far succeeded in making it work.
North Korea is one of the world's poorest countries and struggles to generate enough electricity for lighting and other basic needs.
The statement, carried by North Korea's official state media, said the country's scientists had succeeded in carrying out nuclear fusion.
Laboratory demonstrations of the process, known to release large amounts of energy, are nothing new.
But the North Koreans appear to be claiming to have gone much further, by building what they describe as a "unique thermo-nuclear reaction device".
'Highly unlikely'
The dream of overcoming the huge technical challenges to make nuclear fusion commercially viable has so far eluded scientists in Europe, America and China, but they continue to try because the prize is so great: a cheap and abundant source of energy with little environmental impact.
North Korea's claim that it has completed the fundamental research, putting the technology within its grasp, will be dismissed as highly unlikely unless concrete evidence is produced.
Pyongyang says its latest scientific breakthrough coincides with the birthday of the country's founder, and eternal president Kim Il-sung - not the first time it seems that the laws of nature have been bent in his honour.
According to official biographies, when his son, the current leader Kim Jong-il was born, a new star appeared in the sky.