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.