(Corrects Oct. 19 story headline and first paragraph to 1.6 mln Mate 60 series sold, not just Mate 60 Pro handsets, and clarifies Mate 60 Pro is almost three-quarters of that figure in paragraph 3)

SHENZHEN, China (Reuters) -Huawei Technologies has sold 1.6 million of its Mate 60 series handsets in six weeks, a research firm said, as the Chinese technology giant defies a smartphone slowdown to enjoy strong demand in its high-end smartphone renaissance.

Of those sales, more than 400,000 units were in the last two weeks, the period in which Apple launched the iPhone 15 on the mainland, Counterpoint Research said.

The high end Mate 60 Pro made up almost three-quarters of the Mate series phones sold, Counterpoint said.

In its first 17 days, iPhone 15 sales were down 4.5% compared to the iPhone 14, Counterpoint said, without providing specific figures.

Huawei did not immediately respond to a request for comment.

Huawei made a surprise launch of its premium Mate 60 Pro phone in late August, which many analysts say uses a domestically made chip and marks a breakthrough in the face of years of U.S. technology sanctions against the company.

The handset has been in high demand, with available stock swiftly being bought up as soon as it arrives, "creating the appearance of perpetual unavailability," said Counterpoint senior analyst Ivan Lam.

The overall global smartphone market contracted by 8% to its lowest third-quarter level in a decade on subdued demand for major brands.

Huawei, its former unit Honor, and Transsion Group were the only brands to record year on year growth in that period.

In China August smartphone shipments remained largely flat, rising 0.03% year on year to 18.99 million handsets, according to the China Academy of Information and Communications (CAICT).

(Reporting by David Kirton, editing by Deborah Kyvrikosaios)