Borders around Ceuta and Melilla to be strengthened as EU says it is 'concerned' over country's response to immigrants

Spain is to spend more than €2.3m (£1.89m) fortifying the borders that divide its territories of Ceuta and Melilla from Morocco, in an attempt to deter the thousands of migrants who arrive at the borders of its two exclaves in north Africa, the country's interior minister has announced.

Reinforcements to be added in the coming weeks include lining the six-metre-high fences that surround both cities with a type of mesh meant to "impede anyone from climbing", Jorge Fernández Díaz told reporters.

In Ceuta, an additional 20 Guardia Civil agents will be deployed and a helicopter will now help with the "dissuasion and detection" of migrants. In Melilla, the government will set up three watch towers equipped with heat-sensitive cameras.

The announcement comes as the Spanish government faces criticism from EU officials, who have said they are "very concerned" over the country's response to sub-Saharan Africans and other immigrants who flock to the Spanish territories, desperately seeking better lives in Europe.

Last month, 15 migrants drowned in the Mediterranean after dozens tried to enter Ceuta by swimming around the man-made breakwater that separates Moroccan and Spanish waters. Migrants said that Spanish police had tried to keep them in Moroccan territory by firing rubber bullets at them and spraying them with tear gas as they tried to swim to Spanish land.

Fernández Díaz later said that police had indeed fired rubber bullets, but that they were "fired at the water, not at people". He denied that police actions played any role in the drowning of the migrants.

A court in Ceuta has opened an investigation into the incident, but the ruling People's party used its majority in parliament to block a request by opposition parties for a further investigation by a parliamentary commission.

Each year, thousands of Africans – many of whom have spent years travelling across north and sub-Saharan Africa – try to gain entry into the EU either by swimming along the coast or climbing the three rows of fences lined with razor wire that mark the border between Morocco and the enclaves. Many of them live in rough, makeshift campgrounds on the Moroccan side, waiting for an opportunity to rush the frontier.

After nearly a decade of relative calm, the numbers of migrants attempting to cross into Ceuta and Melilla have risen in the past few years. Around 3,000 illegal migrants entered Spain in the first half of last year, according to government statistics, double the figure for the same period in 2012.

More than 200 migrants managed to scale the triple fence in Melilla last week, whooping with joy and kissing the ground as they celebrated a crossing they hoped would allow them to stay in Europe.

Days later, emboldened by news that Spanish police had been banned from firing rubber bullets and rumours that Spain would soon be reinforcing the fences, some 700 sub-Saharan migrants attempted to cross into Ceuta from Morocco. While many of them were turned away by Moroccan forces, authorities said it was the largest group of migrants they had ever seen attempt to scale the fence at once.

The borders have also been attracting migrants from outside Africa. Last month, Spanish police closed a border crossing into Melilla after being tipped off that a large number of Syrian migrants were going to try to push across.

As tensions rise at their north African borders, Spain's approach to the migrants has earned them criticism, both at home and in the EU. Past weeks have seen hundreds of Spaniards take to the streets in protest, carrying signs reading, "Ceuta: the shame of Europe" and "More bridges. No walls."

The European commissioner for home affairs, Cecilia Malmström, has also expressed her concern, particularly over last month's incident in Ceuta. In a letter to the Spanish government, she asked if the firing of rubber bullets "could have provoked panic among the group of immigrants" and so played a role in the 15 deaths.

Fernández Díaz met her this week to defend the country's actions at the border, arguing that Spain is simply protecting the border on behalf of all of Europe. To reinforce his point that this issue is a European one rather than a Spanish domestic affair, the interior minister asked Brussels for €45m to help ease what he described as an "emergency situation" in Ceuta and Melilla.

The meeting was just the latest in a long list of diplomatic conflicts spurred on by Ceuta and Melilla. The Spanish exclaves have also been a constant thorn in Moroccan and Spanish diplomatic relations. Much like Gibraltar, the residents in the two territories proudly declare themselves loyal to Spain, a country that lies across the sea, rather than to Morocco, the one that surrounds them.

But unlike Gibraltar, where the Spanish government continues to noisily press its claim to the territory, attempts by Morocco to claim Ceuta and Melilla have been quietly ignored.

Instead, the Spanish government has shut down any attempt to draw parallels between the territories, arguing that the situations are completely different and cannot be compared.