BRUSSELS (Reuters) - The European Commission will investigate whether Russia, Brazil and three other countries are flooding the bloc with cheap hot-rolled flat iron and alloy and non-alloy steel products, following a complaint from European rivals.

The EU executive said the probe, opened on Thursday, will focus on the period July 1, 2015 to June 30, 2016.

In addition to Russian and Brazilian iron and steel exporters, the Commission is also targeting those from Serbia, Ukraine and Iran. The companies have been given 15 days to contact the EC with their details.

The European Steel Association (Eurofer), whose members account for more than a quarter of EU iron and steel products, triggered the case with a May complaint.

"The complainant has provided evidence that imports of the product under investigation from the countries concerned have increased overall in absolute terms and in terms of market share," the Commission said in the Official Journal.

The EU, which can impose duties on imports if there is evidence that these are sold at below fair market prices and are damaging the businesses of European competitors, now has 10 anti-dumping investigations underway into steel products.

(Reporting by Foo Yun Chee; Editing by Robert-Jan Bartunek, Greg Mahlich)