A smuggling tunnel the length of seven soccer pitches complete with its own train has been found running beneath the border between Slovakia and Ukraine along with more than 2.5 million contraband cigarettes, the Slovak government said.

Police said the tunnel had possibly also been used to smuggle people into Slovakia, a European Union member state, from Ukraine, but that its main use had been to illegally import cigarettes into the EU bypassing customs duties.

"This tunnel was equipped with a small train, capable of transporting various kinds of goods and we suspect also people," Interior Minister Robert Kalinak told reporters.

"There has been no case like this in this region," he added.

The tunnel was 700 metres (765.5 yards) long and connected a warehouse between the Slovak villages of Vysne and Nizne Nemecke with a newly-built family house in the Ukrainian border city of Uzhorod, Kalinak said.

Tibor Gaspar, president of the Slovak police, said sophisticated mining-technology appeared to have been used to dig out the tunnel, which ran about six metres below ground.

Finance Minister Peter Kazimir said a special tax evasion task force formed by the police and custom officials had been monitoring the Slovak house for weeks.

He said 13,100 cartons containing 200 cigarettes each had been seized in the raid, equivalent to 2.6 million cigarettes.

"We can assume excise tax evasion could reach up to 50 million euros, in case the tunnel was used for a year," Kazimir said.

The owner of the Slovak property was arrested on site along with a truck driver in a different location, police said, adding that a joint investigation with Ukraine would continue since many more individuals must have been involved. (Reuters)