SEOUL - A South Korean fishing boat likely crossed a maritime border into North Korea early on Thursday and is being towed by a North Korean patrol boat to a North Korean port, a South Korean military official said.

The incident took place off the east coast of the Korean peninsula, an official with South Korea's Office of the Joint Chiefs of Staff said.

Contrary to earlier reports it had been captured, the fishing boat with an unidentified number of crew members on board likely experienced a malfunction of its satellite navigation system and strayed north of the maritime border with the communist state, the official said.

It is not likely a case of a North Korean vessel venturing into the South and capturing the ship, the official said.

The incident comes as a South Korean worker has been held for more than 120 days for supposedly insulting the North's political system at a factory park jointly run by the rival Koreas.

The North is also holding two American journalists who were captured at its border with China in March and found guilty of hostile acts against the North.

(Reporting by Jack Kim, Cheon Jong-woo and Christine Kim; Editing by Jonathan Hopfner)