Polish Prime Minister Donald Tusk on Tuesday accused the "Russian state" of attempts to smuggle thousands of migrants from Africa to Europe as Poland plans to fortify its eastern border.

Since summer 2021, thousands of migrants and refugees, mainly from the Middle East, have crossed or attempted to cross the border between Belarus and Poland.

Warsaw and the West have blamed Belarus for orchestrating the influx of migrants with its Russian ally, as part of a "hybrid" attack designed to destabilise the region and the EU.

Speaking to reporters on Tuesday, Polish premier said the intelligence from the country's special services indicated the "Russian state" was to blame for those efforts.

"It is the Russian state, not some murky business, that is behind the organisation of the recruitment, transport and attempts to smuggle thousands of people" into Europe, Tusk said.

He listed Somalia, Eritrea, Yemen, and Ethiopia as countries where Russia seeks to "recruit" migrants to send them to the Polish border by flying them through "one of the Arab countries" to Moscow.

"Currently, several places have been located in Russia, where large groups of migrants organised in this way are concentrated," Tusk said, citing information from services of allied countries, without providing further details.

"More than 90 percent of those who cross the Polish border illegally are people with Russian visas," he added.

Poland announced on Saturday it would spend over 2.3 billion euros ($2.5 billion) on fortifying its eastern border with Belarus and the Russian exclave of Kaliningrad.

The new fortifications "will be an element of dissuasion, a strategy to push back the war at our frontiers," Tusk said on Saturday.

Poland in 2022 erected five-metre-high metal fence along 186 kilometres of its border with Belarus to deter migrants, equipping it with thousands of cameras and motion sensors.

Similar measures have been put in place along its border with Russia.

According to the Polish border guard agency, over 13,000 attempts to cross the border from Belarus have been detected this year.