BEIJING, April 1 (Reuters) - BYD posted a seventh straight monthly sales decline in ​March, according to Reuters calculations, as the Chinese ‌electric vehicle maker struggles with growing competition in the world's largest auto market.

BYD's sales fell 20.5% last month from a ​year earlier to 300,222 vehicles, easing from ​a 41.1% decline in February, the calculations showed, ⁠based on a Weibo post by BYD executive Li ​Yunfei and the company's previous filings.

First-quarter vehicle sales were ​down 30% from a year earlier, the calculations showed.

BYD's sales in its home market have been squeezed by growing competition ​from rivals including Geely and Leapmotor, prompting the EV ​market leader last month to roll out its first major battery upgrade ‌in ⁠six years.

The new lineup, priced above 150,000 yuan ($21,721) - a key threshold in China's hyper-competitive EV market - has raised doubts about its ability to boost sales as ​buyers continue to ​favour cheaper ⁠models.

BYD's vehicle margins fell last year as its annual profit declined for the ​first time in four years, missing estimates.

Overseas ​sales ⁠remain a bright spot, totalling 320,673 vehicles in the first quarter, or 45.8% of the total.

BYD is "highly confident" of ⁠hitting ​its 2026 overseas sales target ​of 1.5 million vehicles, Reuters reported on Monday.

($1 = 6.9058 Chinese yuan renminbi)