SEOUL (Reuters) - Samsung Electronics Co Ltd estimated its January-March operating profit rose 53 percent to 8.7 trillion won ($7.74 billion) as sales of mid-tier smartphones helped the South Korean giant tide over the off-peak season.

The guidance - released ahead of full quarterly results due by April 26 - was better than an average forecast for 8.3 trillion won by 42 analysts polled by Thomson Reuters I/B/E/S.

That spells the end of five straight quarters of record profits for the world's biggest technology firm by revenue.

Samsung estimated its first-quarter sales at 52 trillion won, versus a market forecast for 53.0 trillion won.

(Reporting by Miyoung Kim; Edited by Ryan Woo)