April 20 (Reuters) - Steel Dynamics' first-quarter profit rose on Monday, driven by higher steel prices resulting from tighter supply due to mill outages and imports falling to multi-year lows.

The company's shares were up 1.2% in aftermarket trading.

U.S. steel imports remained at multi-year lows amid tariffs and domestic trade actions, while manufacturing onshoring and regionalized supply chains continued to support demand.

Steel demand during the quarter was driven primarily by the energy sector, followed by non-residential construction, automotive and other industrial markets.

The company posted first-quarter revenue of $5.20 billion, compared with $4.37 billion a year ago. Analysts on average were expecting $5.10 billion for the quarter, according to data compiled by LSEG.

The steelmaker also benefited from lower scrap prices, an essential feedstock for its electric-arc furnace steel mills.

"We remain constructive that market conditions are in place for domestic steel and aluminum consumption to be strong through 2026 and into the following years," CEO Mark Millett said.

Millett said two of the company's three planned cold mills are ramping up operations, while the third is scheduled to be commissioned in the third quarter of 2026.

The Fort Wayne, Indiana-based company's first-quarter profit per share was $2.78, compared with $1.44 a year earlier.

(Reporting by Megavarshini G. Somasundaram in Bengaluru; Editing by Vijay Kishore)