KIEV, Aug. 9 - An informal system of customs controls in Ukraine is causing serious delays to Ukrainian wheat exports, Reuters reported Monday, citing trade and shipping sources.

Dealers in Europe said there was widespread trade talk of several hundred thousand tonnes of Ukrainian grain shipments being delayed by extra customs or documentary checks or sudden non-availability of railway freight wagons for grain transport.

"There is widespread belief in the market that Ukraine is undertaking some deniable form of export slowdown," one trader said.