Bulgaria launched on Tuesday a second attempt to privatise the defence group VMZ Sopot after cancelling the first procedure for lack of investor interest, the privatisation agency said.

Bidders were invited to file binding offers for all 118,000,000 shares in VMZ within the next six months, the agency said in a statement.

These could be strategic investors with experience in the defence production field or consortiums of such investors and smaller companies, it added.

Bulgaria cancelled in January its first attempt to sell VMZ -- its biggest defence firm and the last that is still state-owned -- after just one bidder filed an offer but failed to pay a required deposit.

The latest attempt was said by experts to be the last chance to save the heavily indebted company from insolvency.

Although far from its communist-era glory, VMZ still produces a broad range of missiles and artillery ammunition.

Its 3,000 workers staged several strikes this winter to press their demands for unpaid salaries, social security and healthcare payments.

Lack of strategic investors in previous defence company tenders has led other state-owned firms to morph into joint-stock companies, owned primarily by their managers and staff.

Bulgaria's defence industry exports stood at 300 million euros ($400 million) in 2011, according to latest data by the economy ministry.