Some 400 Tunisian Islamist fighters have returned home from Syria, Tunisian Foreign Minister Mongi Hamdi said Monday. While it was not possible to arrest them, the minister said, local security forces are monitoring them closely since they received combat training abroad and subscribe to a radical ideology.

Hamdi made these statements during a meeting of defense establishment officials, who were discussing ways in which to cope with terrorist threats.

The fighters’ return from Syria to their countries of origin, whether these countries are Arab or European, has become an issue of concern to security agencies and intelligence communities in those countries. They fear that the returnees will establish sleeper cells in their homelands that could strike targets at short notice.

A Jordanian official told Haaretz this week that his country's government, which is extremely worried about the implications of this phenomenon, is keeping close track of traffic on the Syrian border and even arresting suspected radicals trying to cross over either into Syria or in the opposite direction.

The Jordanians have frequently recalled the Lebanese-Iraqi situation, whereby porous borders allowed the establishment of an infrastructure for groups linked to Al-Qaida and global jihadists. Officials in various Arab states believe that this trend has also benefited the regime in Syria, which has adopted a policy of battling terrorism before seeking any agreements, and claims that the fragmented opposition cannot be a partner to any future accord. For its part, the opposition claims that the regime is essentialy providing a hothouse for these same Islamic groups in an attempt to cause further unrest.

In the past week there has been talk among Arab states, and other countries that are defined as supporters of the Syrian opposition, about strengthening moderate forces – chiefly, the Free Syrian Army – and embarking on a military operation that would spur changes on the ground. It is believed that such a move would force a political solution and the removal of Syrian President Bashar Assad from power.