By Reuters

An employee works at a steel processing production line of a factory in Mandi Gobindgarh in the northern state of Punjab, India - REUTERS

(Reuters) -Shares of U.S. steel and aluminium manufacturers jumped in premarket trading on Monday after President Donald Trump announced plans for an additional 25% tariffs on the import of the metals.

Nucor surged 9.5%, Steel Dynamics 6.3%, Century Aluminum 9.4%, while Alcoa added 5.9%.

U.S. Steel gained 7.4%, also on comments from Japan's Chief Cabinet Secretary Yoshimasa Hayashi that Nippon Steel is considering a bold change in plan from its previous approach to buy the U.S. company.

Roughly a quarter of all steel used in the U.S. is imported, the bulk of it from neighboring Mexico and Canada or close allies in Asia and Europe, such as Japan, South Korea and Germany.

Shares in European steelmakers, which account for about 15% of U.S. imports, fell with ArcelorMittal, Voestalpine and Salzgitter all down between 0.6% and 2.5%.

"The major structural challenges that already exist in the German steel sector could be exacerbated by tariffs," DZ Bank analysts said.

ArcelorMittal's finance chief last week said the hit from potential U.S. tariffs would be about $100 million a quarter and that the group had no plans for preemptive shipments.

Shares of Thyssenkrupp, which has said that about 5% of its annual production is exported to the U.S., dipped 0.2% in choppy trading.

Peers in Asia fell after the tariff announcement as well with India's Tata Steel and JSW Steel down 3.2% and 2.3%, respectively.

(Reporting by Christoph Steitz, Paolo Laudani, Isabel Demetz and Medha Singh; Editing by Rachel More, David Goodman and Arun Koyyur)