(Reuters) - European Union member Latvia has deployed 3,000 troops for a previously unannounced military exercise near its border with Belarus this weekend amid an escalating migrant crisis along the Belarusian-Polish border.

       The EU planned to widen sanctions against Belarus over Western accusations, which on Monday it denounced as "absurd", that it is orchestrating a crisis that has left up to 4,000 migrants stranded in freezing forests on its border with Poland.

       European leaders accuse Belarus of mounting "a hybrid attack" by flying in migrants from countries like Syria and Afghanistan and pushing them to cross illegally into EU member Poland. Belarus has repeatedly denied the accusation.

       "We cannot exclude that part of these (migrant) groups will move further north and can reach the Latvian border. We're ready for it," Latvian Defence Minister Artis Pabriks told the national broadcaster.

       The message to Belarus is that the Latvian army movements are "not just for fun", he added.

       The military drill began on Saturday and is scheduled to last until Dec. 12, army spokeswoman Sandra Brale told the BNS news wire. She did not reply to Reuters messages seeking further comment on Monday.

       Polish border guards have reported 5,100 attempted irregular crossings from Belarus so far in November, compared to 120 in all of 2020. Comparative numbers also spiked in Latvia and Lithuania, the two Baltic states that border on Belarus.

       Poland and Lithuania have also reinforced their borders with military forces, and all three countries have secured sections of their frontier with Belarus with razor wire fencing.

       (Reporting by Andrius Sytas in Vilnius; Editing by Mark Heinrich)