Russia is attempting to obtain more weapons from Iran, including hundreds of ballistic missiles, and offering Tehran an unprecedented level of military and technical support in return, Britain's U.N. Ambassador Barbara Woodward said on Friday.

Woodward also said that since August Iran had transferred hundreds of drones – also known as unmanned aerial vehicles (UAVs) – to Russia, which had used them to "kill civilians and illegally target civilian infrastructure" in Ukraine.

Iran denies supplying the drones to Moscow, and Russia has denied its forces used Iranian drones to attack Ukraine.

"Russia is now attempting to obtain more weapons, including hundreds of ballistic missiles," Woodward told reporters.

"In return, Russia is offering Iran an unprecedented level of military and technical support. We're concerned that Russia intends to provide Iran with more advanced military components, which will allow Iran to strengthen their weapons capability," she said.

The Iranian and Russian missions to the United Nations did not immediately respond to a request for comment.

Iran has promised to provide Russia with surface-to-surface missiles, in addition to more drones, two senior Iranian officials and two Iranian diplomats told Reuters in October.

The United States said on Wednesday that it has seen the continued provision of Iranian drones to Russia, but that Washington had not seen evidence that Iran has transferred ballistic missiles to Russia for use against Ukraine.

Woodward spoke ahead of a Security Council meeting later on Friday, requested by Russia, on weapons from the Ukraine conflict that Russia says are "falling into the hands of bandits and terrorists" elsewhere in Europe, the Middle East, and Africa.

She also said that Britain was "almost certain that Russia is seeking to source weaponry from North Korea [and] other heavily sanctioned states, as their overstocks palpably dwindle."

The United Nations is examining "available information" about accusations that Iran supplied Russia with drones, U.N. Secretary-General Antonio Guterres told the Security Council in a report earlier this week, as he faces Western pressure to send experts to Ukraine to inspect downed drones.

Britain, France, Germany, the United States, and Ukraine say the supply of Iranian-made drones to Russia violates a 2015 U.N. Security Council resolution enshrining the Iran nuclear deal.

Russia argues that there is no mandate for Guterres to send U.N. experts to Ukraine to investigate the origin of the drones.

Guterres said in the latest report that the transfer of drones or ballistic missiles – with a range of more than 186 miles – from Iran to another country would require prior approval from the U.N. Security Council.