WARSAW, Aug 9 (Reuters) - A record number of migrants have crossed the Polish border with Belarus since Friday, the Border Guard said on Monday, amid accusations Minsk is using illegal crossings to pressure European Union states. Poland and Lithuania have seen a surge in illegal migration in recent weeks that is so severe the countries have appealed to the EU for help, with the parliament in Vilnius planning an extraordinary session on Tuesday to discuss the issue. Authorities in the countries have accused President Alexander Lukashenko of using migrants to put pressure on the EU to reverse sanctions on the country or to hit back at Poland for giving refuge to Krystsina Tsimanouskaya, a Belarusian athlete who refused to return home from the Tokyo Olympics. read more The Polish Border Guard said in a statement on Monday it had detained 349 illegal migrants crossing the Belarus border since Friday. It said the migrants were probably from Iraq and Afghanistan. Border Guard spokeswoman Anna Michalska said the numbers of migrants detained since Friday were a record. The largest group of 85 people was detained by officers from the Kuznica station on Saturday, according to the statement. This year the Podlasie Branch of the Border Guard, which works on the border with Belarus, has detained 871 illegal immigrants. In 2020 the Border Guard detained 122 illegal migrants crossing the Belarusian border. On Friday, Poland and Lithuania called on European institutions to help them deal with migration. European Union home affairs ministers will discuss the issue at an extraordinary meeting on Aug. 18. read more Lukashenko said that Belarus would retaliate when "hit" and that western countries should not use sanctions against Belarus. "(Sanctions) can have the opposite effect, which is shown by the reality of today"s events on the Belarusian-Polish, Belarusian-Ukrainian, Belarusian-Lithuanian, and Belarusian-Latvian borders," he told a news conference on Monday. Monday marked the first anniversary of an election which opponents said was rigged to let Lukashenko win. Tens of thousands of people took to the streets in the biggest challenge to his rule since he became president in 1994. He says he won the election fairly and responded with a crackdown on opponents in which many have been arrested or gone into exile abroad.