BRUSSELS, ROME AND MADRID — US Defense Secretary Ash Carter's visit to Europe last week inevitably focused on Russian bombing in Syria, but he also stressed the growing danger of instability in North Africa after making stops in Spain and Italy.

Speaking at the NATO defense ministers’ meeting in Brussels, on Thursday, Carter described "the challenges facing NATO's southern flank, including the ripple effects of [the Islamic State in Iraq and the Levant] and state instability in North Africa and the Middle East."

In Spain, Carter visited the Moron de la Frontera Air Base, home to a Marine contingent set up following the 2012 murder of US diplomat Christopher Stevens by militants in Benghazi, Libya, as the country collapsed into chaos. The Special Purpose Marine Air-Ground Task Force (SP-MAGTF) envisages a maximum presence of 2,200 military staff, 500 DoD staff, six MV-22 Ospreys and two KC 130J Super Hercules for supplies and medical evacuation.

After a final agreement on defense cooperation reached last month with the Spanish government, the initial SP-MAGTF crisis response has become permanent and allows for a maximum long-term U.S. military presence at Moron Air Base of 2,200 military personnel, 500 US Defense Department civilian employees and 36 aircraft. («Osprey» and «Super Hercules).

With options for the addition of an 800-strong crisis response force and 14 more aircraft, the contingent is three to four hours from Libya and has already operated in Sudan and trained in Senegal, as well as serving as a US logistics hub during the West African ebola outbreak in 2014.

In June, US F-15 fighters mounted an attack in Libya on Mokhtar Belmokhtar, a jihadist who led a deadly attack on an Algerian gas facility two years ago.

Besides the Moron Air Force, the US has home-ported four Arleigh Burke-class destroyers, equipped with the Aegis guided missile combat system, in Rota as Spain's contribution to NATO ballistic missile defense.

The US is not involved in an EU naval operation, which started on Oct. 7, to capture traffickers who have helped over 130,000 migrants and refugees sail from lawless Libya to Italy this year.

Carter also visited the US air base at Sigonella on the Italian island of Sicily, from where planes flew to bomb Libya in 2011 to assist rebels fighting then leader Col. Moammar Gadhafi.

US Global Hawk UAVs now fly over Africa from Sigonella, and Carter said in Rome that Global Hawks acquired by NATO as part of its Allied Ground Surveillance program would arrive in Sigonella next summer. This summer, a US Beechcraft King Air 350ER flew from the Italian island of Pantelleria in the Mediterranean to remote areas in western Tunisia, to track suspected terrorists, reportedly on behalf of Africom.

Syria Focus

Still, the majority of the NATO conference — and indeed, of Carter's trip abroad — was naturally focused on the situation in Syria, with a number of NATO members condemning Russia's ongoing actions in support of Syrian President Bashar al-Assad.

"Instead of engaging in political transition in Syria, which is needed in this long-suffering country, Russia has chosen to double down on their long-standing relationship with Assad, committing additional capabilities and personnel," Carter said in a speech at NATO.

Those comments were echoed by other European leaders. Federica Mogherini, the High Representative of the Union for Foreign Affairs and Security Policy, cautioned that a military escalation on Russia's part "will lead nowhere."

She added that, for Russia, "fighting alongside the regime" in Syria's bloody civil war will only "prolong the agony" of the conflict.

On the fight against terrorism in Syria, she said the EU had decided "long ago" not to be militarily involved, but added, "Still, we actively contribute with non-military means to the objectives of the global coalition against Da'esh. Our engagement goes from reducing the threats of radicalization and the recruitment of new foreign terrorist fighters in European countries, to working to stop the flow of revenues to Da'esh"

Anna Fotyga, who chairs the European Parliament's influential subcommittee on security and defense, also accused Russia of "trying to destroy" the opposition in Syria rather than fighting IS.

Those concerns seemed to manifest themselves in real terms toward the end of last week, as ISIS fighters for the first time advanced to within a few miles of Aleppo — a key commercial town — after taking a series of villages while rebel forces fighting them were under attack from Russian raids.

"ISIS is exploiting the confusion caused by the Russian bombing of rebels to help its advance on Aleppo," said Thomas Pierret, a lecturer in contemporary Islamic studies at the University of Edinburgh.

By Tom Kington in Rome, Esteban Villarejo in Madrid and Brussels, and Matthew Bodner and Martin Banks in Brussels