BEIJING (AFP) -- North Korean visits to China have multiplied over recent years, a Chinese newspaper reported, underscoring growing political and business links between the isolated nuclear-armed state and its sole major ally.

There were a total of 180,600 visits by North Koreans to China in 2012, nearly twice as many as the 103,900 only three years previously, the investigative Southern Weekly said in its latest edition, citing official data.

"Ordinary people in North Korea are not free to go abroad (as they wish). Therefore, a rapidly growing number of people going abroad usually has certain political significance," the newspaper said.

In 2010 the then North Korean leader Kim Jong-Il came to China twice, suggesting closer political links, according to the report.

Tensions on the Korean peninsula have soared in recent months, with the North carrying out its third atomic test in February, the UN expanding sanctions and Pyongyang's young leader Kim Jong-Un threatening nuclear war against the US and the South.

One state-owned Chinese bank has said it decided to shut a North Korean bank's account, but Beijing has long come under pressure to intervene with its neighbour, which it supplies with vital aid, trade and energy.

The two have longstanding links, and North Korean visits to China for "meetings and commerce" purposes almost tripled from 2009 to 2012, going from 19,400 to 55,200, the Southern Weekly reported.

Journeys in the "labourer" category went up by more than 50 percent, going from just over 50,000 to nearly 80,000, it said, adding the figures were obtained from China's tourism authorities.

North Korean labourers, sent by Pyongyang to earn its much-needed foreign exchange, are travelling beyond the border town of Dandong to more Chinese cities including Shenyang and Dalian in the northeast as well as Beijing, it said.