Moscow (AFP) - Russia said Friday that trucks loaded with oil continue to cross from Syria into Turkey but in lesser numbers thanks to its bombing campaign against Islamic State jihadists.

"Oil tank trucks are continuing to cross the Syrian-Turkish border," the defence ministry said in a statement.

Citing intelligence data, Moscow said the number of oil tankers moving along the so-called northern route towards a refinery in the Turkish city of Batman had gone down.

The same could be seen along the western route leading to Reyhanli and Iskenderun, the two Turkish cities on the Mediterranean coast, the ministry said.

"The number of oil tankers there went down to 265," the statement said.

Moscow said jihadists had been looking for new ways to smuggle oil out of Syria to avoid Russian strikes.

Some of the trucks travelling from Syria are entering Turkey near the Iraqi city of Zakho on the Turkish border, the statement said.

"Despite a significant 'detour', Turkey remains the final point of the smuggling route," the defence ministry said.

Oil tankers going through the so-called northern and western routes are mainly travelling at night, it added.

"Oil tankers are disguised as ordinary trucks and travel in small columns numbering a few dozen vehicles," the ministry said.

Over the past week, Russian strikes destroyed 17 truck columns as well as 37 targets involved in the extraction and refining of oil.

Overall, around 2,000 oil tank trucks have been destroyed since Russia launched a bombing campaign in Syria on September 30. Since its start, Russian armed forces have conducted 5,240 sorties in Syria, the ministry said.

After Turkey shot down a Russian bomber at the Syrian border last month, Moscow accused Turkish President Recep Tayyip Erdogan and his family of involvement in the illegal oil trade with IS jihadists, claims Ankara has strongly denied.

Earlier this month the United States said the amount of oil smuggled into Turkey from areas of Syria controlled by the Islamic State is economically insignificant, with Moscow accusing Washington of turning a blind eye to the trafficking.