BRUSSELS/VILNIUS, Aug 18 (Reuters) - EU countries accused Belarus on Wednesday of conducting "a direct attack" by pushing asylum seekers across its border and, uneasy about the prospect of a surge of Afghan migrants, agreed they need to strengthen their external borders in the future. The European Union accuses Belarus President Alexander Lukashenko of orchestrating the arrival of thousands of people at the borders of Lithuania, Latvia and Poland in retaliation for sanctions imposed on the former Soviet republic. Interior ministers of the 27-nation EU said in a statement to be issued after an emergency meeting that Belarus was seeking to "instrumentalise human beings for political purposes". "This aggressive behaviour ... is unacceptable and amounts to a direct attack aimed at destabilizing and pressurizing the EU," they said in the statement seen by Reuters. The issue has become more acute in the light of the Taliban takeover of Afghanistan that was completed on Sunday. Many Afghans are trying to flee the country, fearing reprisals. EU member states are nervous about a replay of Europe"s 2015/16 migration crisis when the chaotic arrival of more than a million people from the Middle East stretched security and welfare systems and fuelled support for far-right groups. The ministers, without direct reference to Afghanistan, said there was "a need to strengthen the entire external border" of the EU to prevent illegal crossings in the future. BORDER PUSHBACKS The EU accuses Belarus of flying Iraqis to Minsk and then driving them north towards its borders. Lukashenko has said he will no longer hold back migrants due to the sanctions imposed after a disputed presidential election last year and subsequent crackdown on protesters and dissidents. The ministers" statement said countries bordering Belarus and other EU agencies have already been provided with financial and technical assistance to manage the migrant crisis, and more could be sent as required. Lithuania"s Interior Minister Agne Bilotaite said the installation of a fence and a monitoring system could cost more than 500 million euros ($585 million), and that her country was hoping for support from the EU. "The European Commission has allocated 37 million euros of emergency aid to Lithuania to meet immediate needs," she said in a statement. "However, already in September, Lithuania intends to apply for additional financial support." A total of 4,124 people - largely Iraqis - have crossed into Lithuanian territory illegally this year, mostly in July, though only 14 entered between Aug. 5 and 17, as Lithuania and its neighbour Latvia began pushing back those trying to enter. Poland said on Wednesday it had sent more than 900 troops to help secure its border with Belarus. read more The United Nations refugee agency UNHCR has said it is "deeply concerned" by border pushbacks and the Lithuanian Red Cross said it doubted they meet countries" obligations under international treaties on human rights. read more Ylva Johansson, who is responsible for migration and asylum in the EU"s executive Commission, called on member states on Wednesday to ramp up admission quotas for Afghans in need of protection, particularly for women and girls. read more ($1 = 0.8548 euros) Writing by John Chalmers; editing by Philippa Fletcher Our Standards: The Thomson Reuters Trust Principles.