HELSINKI, May 21 (Reuters) - Finland wants the European Union to find common measures to prevent what it calls instrumentalised migration, meaning a flow of migrants arriving from Russia without valid travel documents, Prime Minister Petteri Orpo said on Tuesday.

Finland shut its border with Russia last year to stop a growing number of arrivals from countries including Syria and Somalia, and accused Moscow of weaponising migration against it and the EU, an assertion the Kremlin denies.

Some migrants have still arrived, however, and the Finnish government on Tuesday submitted to parliament a proposal that would allow border agents to return asylum seekers trying to enter from Russia.

"We need to put our national security and the security of EU countries first. We are very aware of our responsibilities to control the European Union's external border," Orpo told a press conference.