An undisclosed number of S-300 surface-to-air missile systems -- which Bulgaria said it is unable to repair -- will be sent to Ukraine, following the decision by lawmakers.

The missiles to be sent to Ukraine are thought to be over 30 years old, said Admiral Emil Evtimov, Bulgaria's Chief of Defence.

Some were even dangerous to keep, since they had not passed maintenance tests, he added.

"These are defective missiles that... Bulgaria cannot repair, but they can be used for Ukraine's air defence," said Hristo Gadjev, the chairman of the parliamentary defence committee.

Ammunition for small arms from police stocks will also be sent, according to the decision, voted through in a closed session Wednesday following a heated debate.

"Everything has been adopted," Delyan Peevski, one of the backers of the initiative, told state radio. "The subject is closed."

EU and NATO member Bulgaria has large quantities of Soviet-style weapons coveted by Ukraine and also produces arms and ammunition.

The country remains historically and culturally very close to Moscow and has been deeply divided over sending aid to Ukraine.

In July, Bulgaria announced it would send about 100 armoured personnel carriers (APCs) to Ukraine, a reverse of its previous policy to refrain from directly supplying arms to the war-torn country.

Apart from the promised APCs, which still need to be delivered, Bulgaria has mostly provided flak jackets and helmets to Kyiv.

This latest proposal was tabled by three parliamentary groups, which between them have 168 out of 240 seats.

The Socialist opposition boycotted the vote, denouncing the decision as a "national betrayal".

On Tuesday, pro-Russian President Rumen Radev criticised the government and the parliament alike for becoming what he called "donors to foreign armies".