HELSINKI (Reuters) - Finland's plan to allow border agents to block asylum seekers from trying to enter from Russia received both praise and criticism on Wednesday, as the country's parliament began debating a draft law.

The government on Tuesday proposed emergency legislation that would allow border guards to reject asylum requests and push back migrants trying to cross Finland's 1,340-km (830-mile) border with Russia. Finland believes Moscow is promoting migration in retaliation for Helsinki joining the transatlantic alliance NATO that backs Ukraine against Russia.

Moscow denies the allegation.

Before Finland closed its eastern border stations last December, more than 1,300 migrants from third nations including Syria and Somalia had made their way to Finland from Russia.

Since then, only a few dozen migrants have arrived from Russia through thick forest along the border but Helsinki fears numbers could grow again.

The so-called push-back law would be useful, several lawmakers said during debate.

"In principle, we think it is a good thing that the government has set out to draft this type of law," said Tytti Tuppurainen, member of parliament for the largest opposition group, Social Democrats.

The second-largest opposition group, the Centre Party, called the government's proposal "absolutely necessary".

It was not immediately clear if the proposed law, which requires a five-sixths majority, will pass in a plenary vote that has not yet been scheduled.

Its strongest opponents include members of a smaller opposition group, the Left Alliance, which holds 11 of parliament's 200 seats.

The proposal was slammed by some legal scholars.

Martti Koskenniemi, professor emeritus of international law at the University of Helsinki, said it conflicted with Finland's constitution and its international human rights commitments, in particular the principle of not returning asylum seekers to a country where they would be in probable danger.

Koskenniemi said the law would grant border guards "completely unsound" powers to judge which migrants might be particularly vulnerable or have reason to fear the death penalty or torture in their home countries.

"It is unheard of that a Finnish authority would be allowed to make on the basis of a gut feeling such judgements that are not administrative decisions and cannot be appealed," he told Reuters.

Finland's non-discrimination ombudsman told Reuters that states had throughout history used migrants to put pressure on each other.

"This is not new or exceptional," ombudsman Kristina Stenman said. She added that it would be alarming if Finland refused to receive asylum applications at its borders.

(Reporting by Essi Lehto and Anne Kauranen in Helsinki; editing by Rod Nickel)

By Anne Kauranen and Essi Lehto