Chinese ships defy Vietnam's demand to vacate gas field area.

A Chinese research ship and five escort vessels are in Vietnam's exclusive economic zone (EEZ) close to gas blocks operated by Russian firms in the South China Sea, despite Vietnam's demand to leave. China claims most of the energy-rich waters of the South China Sea, including areas that are within Vietnam's EEZ. The current dispute is over gas fields operated by Russia's state-owned firm Zarubezhneft. The incursion represents a worrying escalation, according to experts.