Both ministers were on the ground in southeast Estonian Monday to get an overview of the situation, at a time when migratory pressure has been exerted on the EU's eastern frontier by Belarusian dictator Alexander Lukashenko.

Defense minister Kalle Laanet (Reform) said that: 'The EDF relies upon its reservists, and Okas 2021 confirms the fact that the forces are quick and able to respond in all situations.

"Further co-operation with the PPA will actually strengthen the security of the state border – this is a textbook example of broad-based national defense approach,' Laanet continued, according to a ministry press release.

He also thanked all the reserve troops participating the exercise, for their contribution to Estonia's security.

The PPA holds the border guard role in addition to other policing duties, following a merger of the two, previously separate functions, around a decade ago.

Meanwhile Minister of the Interior Kristian Jaani (Center), under whose remit the PPA lies and a former policeman himself, said that: 'This exercise is important to train co-operation between the EDF and the PPA in a situation where we have to respond quickly to possible illegal activities at the border."

"I confirmed today that the organization of the exercise is impeccable and extremely professional. The installation of temporary barriers is going smoothly, except for difficult weather conditions in some places," he added.

"It is also a pleasure to acknowledge that the troops have reached combat readiness. This shows that Estonia is united and the people whose job is not to guard the border on a daily basis are ready to come and contribute at very short notice. This is broad-based national defense,' Jaani went on.

The two ministers had been visiting the site of the weekend's construction work which saw razor wire installed along those segments of the border which are not already cordoned.

While Okas ("Quill") is an annual snap event involving EDF reservists, this year's brought particular urgency with the migrant crisis on the Belarusian border with Poland, Lithuania and Latvia, and amid reports that a possible second route may be opened up via flights from the middle-east to Pskov, which is just 30km from the Estonian border.

This year's exercise as noted was also a joint military-civilian exercise.

Col. Tarmo Metsa, Commander of the EDF's 2nd Infantry Brigade, PPA Southern Prefecture chief Lt-Col. Vallo Koppel and Paavo Mikson, PPA chief at the Piusa Cordon, briefed the two ministers on the exercise and the situation on the eastern border.

Much of the land border concerned lies in the southeast of the country, though a dry river bed linked to the Narva river in the Northeast of Estonia has also seen similar fortification.

Jaani said Monday that the permanent border work, the subject of long delays and politicking, will be concluded as quickly as possible, with 2025 the deadline mentioned.

One aspect of erecting permanent border infrastructure is that it would be a tacit recognition of the present-day Estonian-Russian border over and against that of the 1920 Treaty of Tartu, which lay somewhat to the east and included towns such as Petseri, in the southeast (present-day Pechori, in the Russian Federation) and Jaanilinn, on the other side of the Narva river (literally translated as Ivangorod in its modern appellation).