Rewrites to add detail, changes headline, paragraphs 1-2, 5, 8-9

WARSAW, May 19 (Reuters) - Polish officials have seized 5 metric tons of tyres for Boeing passenger planes that were due to transit through Belarus and Russia, in what Poland's tax and customs office on Monday said constituted a breach of European sanctions.

Western countries have imposed broad-ranging sanctions against Russia and its ally Belarus since Moscow's February 2022 full-scale invasion of Ukraine. Heavily reliant on foreign-made planes, Russia's aviation industry is struggling to provide enough planes to meet demand for air travel.

"Officers... discovered during the inspection of a truck in Koroszczyn that the driver was transporting tyres used in Boeing civil planes instead of the declared car and bus tyres," Poland's National Revenue Administration said in a statement.

"The sender of the goods was a company from Spain, and the recipient was from Azerbaijan. Criminal fiscal proceedings were initiated in connection with customs fraud. The sanctioned goods were detained."

It noted that the transit of such goods through Belarusian and Russian territory is subject to European sanctions.

The statement did not identify the manufacturer of the tyres. Boeing BA.N did not immediately respond to an emailed request for comment.

Shortly after the invasion in 2022, Boeing said it was suspending parts, maintenance and technical support for Russian airlines as well as major operations in Moscow. It also said it was strictly adhering to export controls and restrictions.

After an initial shock, Russian airlines established new means of accessing foreign parts. Customs records show items such as cabin pressure valves and landing gear arriving in Russia through middlemen in countries that have not endorsed sanctions on Moscow, including Tajikistan, the United Arab Emirates, Turkey, China and Kyrgyzstan.

A person working in Russia's aviation sector said airlines have mainly solved the spare parts issue, although the roundabout routes are more expensive and shipments take longer to arrive.

(Reporting by Anna Wlodarczak-Semczuk in Warsaw and Gleb Stolyarov; additional reporting and writing by Alexander Marrow in London; Editing by Christian Schmollinger and Peter Graff)

((anna.wlodarczak@thomsonreuters.com;))