VILNIUS, Aug 10 (Reuters) - Latvia declared a state of emergency along its border on Tuesday and Lithuania decided to erect a fence in new measures to deter migrants they say Belarus is encouraging to cross illegally in order to pressure European states. Rising numbers of migrants have reached Lithuania, Latvia and Poland, which accuse Belarusian President Alexander Lukashenko of using the issue to press the EU to reverse sanctions. read more Poland says Belarus is retaliating against Warsaw"s decision this week to give refuge to Krystsina Tsimanouskaya, a Belarusian athlete who refused to return home from the Tokyo Olympics. Belarus in May decided to let migrants enter Lithuania in retaliation for EU sanctions imposed after Minsk forced a Ryanair flight to land on its soil and arrested a dissident blogger on board. Lukashenko said Belarus would not become a "holding site" for migrants from Africa and the Middle East. On Tuesday, the Latvian government declared a state of emergency in border areas, which allows its military and police to support border guards. The border guard, armed forces and police will be authorised to instruct illegal immigrants to return to the country they came from, and use physical force if they refuse, the Baltic News Service (BNS) said. The state of emergency runs from Wednesday until Nov. 10 and requires the approval of parliament, which is expected on Thursday. Some 283 people have been detained for illegally crossing into Latvia from Belarus since Aug. 6, BNS said, bringing the total for the year to 343 people. In neighbouring Lithuania, parliament voted to build a four-metre (13 feet) metal fence topped with razor wire on 508 km (316 miles) of the 670 km border it shares with Belarus. "Without this physical barrier, it is impossible to protect our borders, it is very clear," Interior Minister Agne Bilotaite told Reuters. The Lithuanian parliament also voted to allow the military to patrol the border alongside frontier guards and to turn back people deemed to have crossed illegally. Those wanting to claim asylum must now do so at an official border crossing or at an embassy. So far this year 4,026 people have illegally crossed into Lithuania, a country of 2.8 million, from Belarus, the Lithuanian interior ministry said last week, compared with 74 in total in 2020. Most come from Iraq, followed by the Republic of Congo and Cameroon, according to the Lithuanian Border Guard. Lithuania says Belarus allows them to head for the Lithuanian border after they have flown to the Belarusian capital, Minsk.