Mazda spent 17.8 billion yen ($184 million) to buy back 6.8 percent of its own shares from cash-hungry Ford Motor, the Japanese automaker said Wednesday. Several other companies bought smaller stakes.

The move came a day after Ford said it's slashing its stake in Mazda from an earlier 33.4 percent to 13.8 percent. That would still make Ford the top shareholder in Mazda, with which it has...