Russia has blocked the transit of Ukrainian goods heading to other countries, Kiev officials said Saturday after the two neighbouring nations imposed food embargoes in their mutual trade war.

"The transit of Ukrainian goods has not yet begun", having been blocked since the start of the new year, the spokeswoman for Ukraine's infrastructure ministry, Kristina Nikolayeva, told AFP.

The ministry said that since January 1, under new Russian regulations, Ukrainian goods headed for Central Asia or China can only enter Russia via Belarus. They must also be sealed to prevent them from being unloaded in Russia.

A Russian embargo on Ukrainian food imports took effect on January 1, with Kiev issuing mirror sanctions in response.

Moscow has also barred Ukraine from a free trade zone linking numerous ex-Soviet countries.

Russia introduced the latest measures on transit of goods without explaining how they should be implemented, with officials absent during public holidays lasting until Monday, said Nikolayeva.

"They brought in these transit rules but didn't prepare a mechanism for how exactly this will work: what kind of seals are needed, what kind of control measures are needed. As a result Russia is not letting Ukrainian trucks across its border," she said.

At present, "we are recommending our carriers not to send anything in that direction," Nikolayeva added.

Ukraine's trade representative Natalia Mykolska has complained that the transit problem is holding up trade with partners such as Kazakhstan, Turkmenistan, Kyrgyzstan, Azerbaijan and Mongolia.

Ukrainian Prime Minister Arseniy Yatsenyuk on Wednesday discussed the problem with his Kazakh counterpart Karim Massimov, the government press service said.

Yatsenyuk said he would inform the World Trade Organisation of the "unlawful actions of the Russian Federation regarding the transit of Ukrainian goods" and would ask the global trade body to "respond to such actions."

Kiev meanwhile is seeking alternative transit routes for its goods that bypass Russia.

Ukraine intends to ship a test delivery to China on Friday across the Black Sea and then via Georgia, Azerbaijan and Kazakhstan, the infrastructure ministry said.

Russia and Ukraine are experiencing an unprecedented crisis in relations after a pro-Western government took power in Ukraine in 2014 followed by Russia's annexation of Crimea and the conflict with pro-Russian separatists in eastern Ukraine.