"Border guards have arrested four men linked to foreigners, who wanted to blow up the Iran-Europe railway with twenty kilos of TNT (Trinitrotoluene)," said Mohammad Ali Zaker, the border guards' chief in the town of Khoy.

Iran's sole railway link to Europe is through Turkey and has a weekly passenger train to Istanbul.

Zaker said the men, known "rebels" in the northwestern Azarbaijan province, had confessed but did not specify when the arrest took place.

"One of the men arrested was a former member of the outlawed Democrat Party," he said in reference to the separatist group the Kurdistan Democrat Party of Iran.

Zaker did not specify the background of the other men.

Last August Iran arrested five Iranian Kurdish militants of the Kurdistan Democrat Party of Iran as well as four men from neighboring Turkey's Kurdistan Workers' Party (PKK) in clashes with the police.

Iran has been battling infiltrations by Pejak, a Kurdish group linked to the PKK, and the Kurdistan Democrat Party of Iran from the Kurdish regions in Turkey and Iraq over the past year.