The likelihood of a fourth nuclear test by North Korea is "very high," a Chinese state-run media reported Wednesday, citing an unnamed source, with the North showing heightened activity at its nuclear test site. The Global Times, published by the Chinese Communist Party's official People's Daily, quoted the unnamed source as saying, "Given the attitude of North Korea's foreign ministry, the possibility that North Korea proceeds with its fourth nuclear test is very high."    The source did not elaborate further, and it is unclear whether the source's assumption is based on intelligence.