Samsung Electronics saw its fourth straight quarterly decline in the Japanese smartphone market in the third quarter, according to industrial data.

The nation’s leading handset maker sold 1 million units of its overall smartphone lineup in the July-September period, posting a 9.9 percent market share, independent research firm Strategy Analytics said Sunday.

The sales figure continued Samsung’s slide from 1.9 million units in the fourth quarter of 2012, 1.4 million in the first quarter of 2013 and 1.3 million in the second quarter.

An industry source said the sluggish sales were largely due to the launch of rival Apple’s newest iPhones, and local companies’ revival in the market.

Apple sold 3.8 million units of its iPhone 5S and 5C in the same period, dominating the market with a 38.1 percent share even though the newest models were only released Sept. 20, the source said.

Experts attributed Apple’s growth to the combination of product quality and NTT Docomo’s dominant position in the market. This was the first time for Apple to partner with Japan’s No. 1 telecom operator as the handset maker used to supply its products exclusively to KDDI and Softbank.

NTT Docomo now appears to be distancing itself from Samsung by excluding it from its main smartphone suppliers for winter promotions.

Following Apple, Sony was ranked second with an 18.9 percent market share, selling 1.9 million units, and even Sharp outsold Samsung by 100,000, holding the fourth place in the local market.

“Considering that Korean companies like Samsung and LG have led the long term evolution market, its sales drop in the market is a sign for concern,” an industry source said. “Samsung should also contemplate developing diversified strategies apart from NTT Docomo.”

By Shin Ji-hye (shinjh@heraldcorp.com)