The number of boats believed to originate in North Korea that drifted ashore on Japanese coasts between last October and March this year fell 90% from a year earlier, the Japan Coast Guard said Thursday.

The number of such boats found in the six-month period totaled 13, down from 141 the previous year, the coast guard said. An expert on the Korean Peninsula situation said the plunge was believed to have been caused by the coronavirus pandemic.

"It appears that North Korea, which wants to maintain thorough border controls against the novel coronavirus, is refraining from conducting illegal fishing operations in the Sea of Japan," said Yusuke Fukuyama, a professor at Hokuriku University.