The Apple iPhone 7 outsold all other smartphone models globally during the first six months of 2017, followed by the iPhone 7 Plus, according to a report from IHS Markit.

iPhone models remain the most popular smartphones, maintaining their bestseller positions since launching.

The Samsung Galaxy Grand Prime Plus held the number three spot, followed by iPhone 6s and Galaxy S8 in in fourth and fifth places, respectively. Galaxy S8 Plus was the number six best seller, with slightly less volume than the Galaxy S8.

Flagship models from Apple and Samsung had sluggish sales in the first half of 2017, IHS Markit analysts said. Although the latest iPhone models secured top positions, shipment volume declined compared to their respective predecessor models, the iPhone 6s and 6s Plus, during the same period in 2016. The smaller-screen 4.7-inch display iPhone models ranked in the top positions in first half of three consecutive years beginning in 2015. However, their market share continues to fall, dropping from 10 percent in 2015 to 7 percent in 2016, and 5 percent in 2017.

Meanwhile, the Samsung Galaxy S8 flagship series recorded a smaller shipment volume this year. "This is likely because Samsung began selling the Galaxy S8 and S8+ models in April, a month later than last year's launch of the S7 series," said Jusy Hong, associate director - mobile devices for IHS Markit. "The shipment ranking of the Galaxy S8 Plus fell to number six, compared to the fourth-place Galaxy S7 Edge in 2016."

Five Samsung models, four Apple models, and one Oppo model ranked in the top 10 most-shipped smartphones in the first half of 2017.

The number of smartphone models with more than a million shipments per month increased in the first half of this year to 22 from 17 in 2016.

Among the 22 top-shipping models so far this year are eight Chinese models that shipped more than 6 million units in H1 2017: five from Oppo, two from Xiaomi and one from Huawei, IHS Markit reported. Samsung had 10 models that shipped more than one million units per month respectively, while Apple had four.