Sweden's left-leaning government is reintroducing a military draft for both men and women because of what Defence Minister Peter Hultqvist calls a deteriorating security environment in Europe and around Sweden.

The country did away with the draft seven years ago, at a time when only men were eligible for conscription.

"We have had trouble staffing the military units on a voluntary basis and that needs to be addressed somehow," Swedish Defence Minister Peter Hultqvist told public service radio SR.

"Therefore it is necessary to reintroduce conscription."

Under the plan approved Thursday, at least 4,000 18-year-olds could be called up each year, starting Jan. 1. The policy affects residents born after 1999, though only a minority will be selected to serve.

As in the current system, Swedes will still be able to volunteer for military service.

The Nordic country mothballed compulsory military service in 2010, but military activity in the Baltic region has increased since, in the wake of Russia's annexation of Crimea in 2014, prompting Sweden to step up military preparedness.

Sweden, which is not a NATO member, is upgrading its military, with a sharp hike in spending, and has reassigned troops to the Baltic Sea island of Gotland, besides urging local governments to step up contingency planning for a future war.