* S.Korea Note 7 sales to restart on Oct 1 vs Sept 28 previously
* S.Korea recall progress slow, triggered delay - Samsung
* Half of affected S.Korea customers turned in their devices (Updates with comments from Samsung, background on ongoing recall)
SEOUL, Sept 25 (Reuters) - Tech giant Samsung Electronics Co Ltd 005930.KS said on Sunday it was delaying the start of new Galaxy Note 7 smartphone sales in South Korea by three days to Oct. 1, a move it says is needed for speedy completion of the ongoing recall in the country.
Samsung announced on Sept. 2 a recall of at least 2.5 million Galaxy Note 7 smartphones in 10 markets, including South Korea, due to a faulty battery causing the phones to catch fire, offering refunds or replacement devices using safe batteries.
The firm hopes to complete the recall quickly and restart sales in the fourth quarter to salvage earnings, but the latest hitch in South Korea underscore continuing challenges in those efforts.
Though product exchanges in South Korea began on Monday, only about 200,000 affected customers have turned in their devices - which Samsung says represents half of affected customers and a recall pace that is much slower than other markets such as Singapore and the United States.
"The recall rate will likely fall sharply should new sales have resumed on Sept. 28," the company said. Affected customers would no longer be able to exchange their devices through domestic carriers starting on Oct. 1, making the process more difficult.
Samsung hopes to restart new sales in affected markets once it makes enough progress with the recalls, having announced plans to restart sales in Australia and Singapore in October, but the nearly month-long recall process has provided additional stumbles and embarrassment for the firm.
Continued reports of Note 7 fires and damages after the recall announcement, along with warnings or outright bans from aviation authorities on the use or charging of the Note 7 on aircraft, forced Samsung to ask affected customers to immediately turn off their phones to prevent further damage.
Samsung apologised on Sunday for the confusion caused by the delay and said it would do its best to resolve the current Note 7 situation quickly.