The United Nations said on Saturday it was concerned by the return to Liberia of mercenaries and Ivorian fighters and had reinforced its forces to patrol the long border between the two countries, according to Reuters. Liberian mercenaries were allegedly hired by supporters of former Ivorian president Laurent Gbagbo during the four-month post-election conflict which ended with Gbagbo's capture in April. The government of Ivory Coast President Alassane Ouattara has said Liberian mercenaries killed about 220 people, mostly civilians as they fled towards the Liberian border. "Yes of course we are concerned in Liberia about the return of alleged Ivorian fighters and Liberian mercenaries," the UN Secretary General's special representative to Liberia, Ellen Margrethe Loj, told a press conference in Dakar. "The first concern is the weapons that might be transported across the border. We have had a few incidents in some towns at the border area where AK-47s have been used in armed robberies," she said after a meeting of UN heads of peace missions in the West Africa region. "We don't know if their intention is to seek refuge only or to take part in illegal activities in one or the other side of the border, so we have to find out what their intentions are," she said. Loj said the UN had reinforced its forces along the border and increased cooperation between security forces of the two countries. The 700 km border is mostly dense rainforest with little infrastructure and is difficult to monitor. The UN had said over 180,000 Ivorian refugees fled to Liberia because of the conflict. Liberia is recovering from 14 years of intermittent civil war and plans to hold a constitutional referendum and presidential elections by the end of the year.