“It’s clear that what we are confronted with here is a demonstration of state terrorism,” he told a news conference.
Thousands of migrants are stuck at the border in freezing weather, attempting to enter EU member Poland.
The EU has also accused Belarus’s leader of provoking the crisis.
But Alexander Lukashenko, who won a largely discredited election last year, denies claims Belarus is sending people over the border in revenge for EU sanctions.
The migrants – mostly from the Middle East – are mainly young men but there are also women and children. They are camping in tents just inside Belarus, trapped between Polish guards on one side, and Belarusian guards on the other.