In a press release issued last night, the ministry expressed its concern over the escalation of tension in the Crimean peninsula in the south of Ukraine, and said it was closely following the developments.

Foreign Minister Karl Erjavec will make a statement on the situation in Ukraine in Naklo near Kranj at 2 PM on Sunday.

Meanwhile, the opposition Democratic Party (SDS) has joined a call by the European People's Party (EPP) for Russian President Vladimir Putin to stop the build-up of Russian troops in Ukrainian territory.

The SDS moreover urged calling emergency sessions of EU and NATO on the developments in Ukraine without delay, expressing its expectation that the two organisations would help protect Ukraine's sovereignty.

"We demand of the Slovenian government to get actively involved in the efforts to find a peaceful solution to the situation. Crisis meetings of the EU and NATO must be called without delay. Waiting for Monday can only worsen the situation," the SDS said.

This is after the EU's foreign policy chief Catherine Ashton called an emergency session of EU foreign ministers on the Ukraine crisis for Monday.

The Slovenian Foreign Ministry had advised against any non-urgent travel to Ukraine already a few days ago.

The tension escalated after the upper chamber of the Russian parliament on Saturday approved deployment of Russian troops in Ukrainian territory.

Ukraine put its army on full combat and stepped up security at key sites, including nuclear plants.