Bulgaria has devoted vastly bigger resources than Germany to help Greece manage its irregular migrant problem.

An internal document sent by the Danish EU presidency to the EU Council in late April - and seen by EUobserver - outlines how individual member states participate in the so called Poseidon operation run by the EU's Warsaw-based border control agency, Frontex.

Frontex described the criminal networks as well-organised big businesses. (Photo: Hans Op De Beeck)

Poseidon was launched in early 2011 and brings together border guards from 23 member states and associated countries in the Schengen passport-free-travel agreement. Member states send their experts and equipment to assist Greek border guards either on a bilateral basis or as part of a larger operation co-ordinated by Frontex.

Among the revelations is the mixed nature of assistance from member state to member state. Some have bilateral agreements with Greece while others work only with Frontex or both.

Specialised tracking dogs, mobile thermo vision systems, helicopters, terrain vehicles and night vision technologies are among some of the tools and services provided.

Bulgaria is one of the more active member states. Despite sharing a border with Turkey, few migrants attempt to cross there. Frontex reports that only a small number of nationals claiming to be from Iraq, Turkey, Palestine and Syria attempted to enter Bulgaria illegally.

Meanwhile, Sofia sent 69 experts in border surveillance, border control and service dog handlers to Greece last year. Another seven Bulgarian experts were stationed at the international co-ordination centre in Alexandroupolis, a city located some 40 km from the Turkish border.

The Bulgarians also supplied 14 mobile thermo vision systems, four manual thermo vision systems, 16 off-road vehicles and four dogs.

For 2012, the Bulgarians have reduced the number of border surveillance experts to 20, but increased the number of dogs and mobile thermo vision systems. They are also supplying 29 patrol cars, 10 manual thermo cameras and sending 10 experts to Alexandroupolis.

The German federal police currently have 10 officers stationed along the Turkish land border. The officers are tasked with area surveillance using thermal imaging and night vision technology.

At the border, they help control trans-border traffic and focus on finding migrants hidden away in vehicles possibly destined for Germany.

The Germans have also agreed to increase the personnel of the federal police for bilateral co-operation in 2012. This includes strengthening support for and co-operation with the Greek police and the Hellenic Coast guard along the Evros river, airports and seaports.

The Poles deployed 25 border guards, two dogs, a helicopter and six service vehicles and are willing to provide additional assistance if requested. The Romanians started participating in the joint-land operation at the end of March and sent 15 border patrol experts and eight vans.

The Austrians sent 48 border guards as well as one infrared-camera vehicle and will station two permanent officers as well as one Frontex support officer.

Slovenia has opted out and will not send any experts on upcoming missions to Greece due to "financial constraints." Last year, they sent two border surveillance experts and deployed a patrol car and a portable thermo vision device.

Finland has no intentions of establishing bilateral co-operation with Greece on border management but is instead working under Frontex. They sent 14 border experts in March for a mission that ends in December. Along with the experts, Finland provided four border guard dogs.

For its part, Frontex claims the border is under control but that attempted border crossings from Turkey into Greece continue.

"The level of detection of migrants is very high and is estimated to be around 90 percent," a Frontex spokesperson told EUobserver on Tuesday (May 22).

"The border is controlled ... the question is why are people still arriving in such large numbers," she added.

The flow of migrants, many arriving through organised criminal networks, continues along the river. Some, for example, fly in from Rabat to Istanbul on budget airlines and then pay the equivalent of €5 for a bus ride to the border crossing at Ipsala.

Frontex described the criminal networks as well-organised big businesses. "It's a machine," said the spokesperson.