China's markets return from a week's break on Wednesday to a fresh trade dispute with the United States and ructions in the global artificial intelligence sector. Investors said they are watching for what Beijing would do to bolster confidence.

As Trump’s new 10 percent tariffs on all Chinese imports took effect, China hit back with tariffs and sanctions of its own.

China’s tariff increases and other countermeasures were mostly symbolic and apparently designed to project strength while leaving the door open to talks.