Toyota Motor Corp., in a bid to reduce its risk from potentially lethal air-bag inflators supplied by Takata Corp., will buy millions of them from smaller parts-maker Nippon Kayaku Co., people familiar with the matter said.

The carmaker asked the second-tier supplier last month to increase production so it can supply Toyota with more than 13 million inflators from next July until 2020, said a person with direct knowledge of the deal and a second individual who was briefed on it.

The move is the most proactive yet by manufacturers affected by the world's biggest automotive recall, which has prompted more than 10 automakers to recall tens of millions of vehicles since 2008 to replace Takata air bags.