RUSSIA is seeking an official explanation from its ally Serbia over reports that the Balkan country has delivered thousands of rockets to Ukraine to fight the ongoing invasion by Moscow’s forces.

Russian Foreign Ministry spokeswoman Maria Zakharova has expressed her “deepest concern” at the reports, which first appeared in pro-government Russian media last month.

In a statement posted on the ministry website on Thursday, Ms Zakharova said: “We are following this story,” adding that Serbia’s possible arming of Ukraine represented a “serious question” for Moscow’s relations with Belgrade.

According to the Russian reports, a Serbian state arms factory recently delivered some 3,500 missiles for Grad multiple rocket launchers, which are used by both the Ukrainian and Russian militaries.

The 122mm rockets were allegedly transported to Ukraine via Turkey and Slovakia.

Serbian Defence Minister Milos Vucevic has denied that  his country exported the missiles to Ukraine but left open the possibility that they could have arrived there via a third party.

Mr Vucevic said: “If private companies buy weapons in third states’ markets and then sell them to other companies in other countries, that is not a question for Serbia, that is international trade.”

Serbia is Russia’s closest ally in Europe, with close historic, religious and cultural ties and has refused to impose sanctions on Moscow over the invasion of Ukraine.

Meanwhile, Hungary further delayed a vote on supporting Sweden and Finland’s applications to join Nato until a parliamentary session beginning on March 20.

Hungary and Turkey are the only Nato members that have not yet approved the two Nordic countries’ bids for membership of the Western military alliance.

Hungarian Prime minister Viktor Orban has said that he is personally in favour of the two countries joining Nato but he alleges that the governments in Stockholm and Helsinki have “spread blatant lies” about his country by criticising its record on democracy and the rule of law.

In a radio interview on February 24, Mr Orban confirmed that Hungary would send a parliamentary delegation to Sweden and Finland to seek “clarification” on such issues before the ratification could come to a vote in parliament.

A unanimous vote of all 30 Nato members is needed to admit new countries. Hungary appears to be following Turkey in leveraging this requirement to demand an end to criticism of its authoritarian government.