Major car makers are accelerating recalls and directing dealers to stop sales of vehicles with potentially dangerous defects amid an aggressive safety clampdown by auto regulators and others in the U.S., Japan and China.

The latest move: Toyota Motor Corp. on Wednesday issued a massive recall of nearly 6.4 million vehicles world-wide. The action covers five separate problems and 27 different models including such globally popular cars as the Corolla, Yaris and Matrix compacts, and RAV4 and Highlander sport-utility vehicles....