The UN has warned Spain over plans to instantly deport migrants who climb over the border fence into its north African territories, saying Spain could end up breaking international law.
"UNHCR is concerned over a proposal by Spain to legalise automatic returns of people trying to cross border fences into its enclaves of Ceuta and Melilla," UN refugee agency's spokesman William Spindler said.
Mr Spindler told reporters that UNHCR understood the "complexity" of border management in the two enclaves, which are tucked into Morocco's Mediterranean coast.
However blanket, on the spot deportations could fall foul of the 1951 Refugee Convention, an international treaty protecting people who flee their homelands, he said.
"UNHCR stresses the importance of permitting access to territory to seek international protection."
The two Spanish cities - which are the only land borders between the European Union and Africa - have seen a sharp increase in numbers of illegal immigrants aiming to head into Europe itself since 2013.
Spain last week announced that it would pass a legal amendment authorising police to expel migrants who climb the fence around Melilla and Ceuta, without giving their asylum claims a hearing.
Mr Spindler said that around two thirds of those trying to cross the seven-metre, triple-layer border fence were from countries torn by war, violence and persecution, including Syria, the Central Africa Republic and Mali.
In 2013, around 4,200 people entered the enclaves illegally by land and sea, he said.
"So far this year, over 5,000 people have arrived, including 2,000 people fleeing the conflict in Syria, of whom 70 percent are women and children," he added.
Mr Spindler also raised concerns about what he said was the growing use of violence at the border to deter migrants and asylum-seekers from trying to enter.
Meanwhile, European Union border control officials met in Brussels to discuss how best to deal with an increase in the number of migrants trying to reach Europe.
The conference took place as Italy prepares to hand responsibility for patrolling the Mediterranean to a new EU force called Operation Triton.
The European Commission said the operation will help but not replace "continued substantial efforts" by Italian authorities.
Italy has long demanded more help from other European countries to help with increasing number of migrants making the dangerous crossing in flimsy and crowded boats, as they flee conflict and economic hardship in the Middle East and Africa.
A record 3,072 migrants have died trying to cross the Mediterranean so far this year, according to the International Organisation for Migration.
Over the past year, Italian warships are believed to have rescued 150,000 migrants who have been trying to reach Europe by boat.
Britain has said it will not support the EU search and rescue operations.
The British Foreign Office said that the government's position had been laid out in a response to a question published by the House of Lords website on 15 October.
"We do not support planned search and rescue operations in the Mediterranean," foreign office minister Joyce Anelay wrote in the response.
"We believe that they create an unintended "pull factor", encouraging more migrants to attempt the dangerous sea crossing and thereby leading to more tragic and unnecessary deaths."
The British government's position is to focus on "countries of origin and transit" and tackle people smugglers instead, she added.
