Istanbul: Turkish President Recep Tayyip Erdogan said Friday he warned France about the cement company Lafarge's ties to terror groups in northern Syria.

"When I explained how the cement giant called Lafarge supported terrorist organisations in northern Syria... the French did not understand," he said.

Erdogan said he had also informed French President Emmanuel Macron.

"I told this to Macron as well. It has become the most important issue on France's agenda at the moment," he said.

"Lafarge emerged as one of the most important institutions supporting terrorism."

Lafarge pleaded guilty in a US court Tuesday to paying millions of dollars to the Islamic State group and other jihadists in war-torn Syria between 2013 and 2014, and agreed to a $778 million fine over conspiring to provide material support to US-designated "foreign terrorist organisations".

The US Justice Department said company executives, including former chief Bruno Lafont, knew of the arrangement with the jihadists.

After the settlement, Lafarge now faces the possibility of the introduction of evidence from the US prosecution into a separate French case over similar charges.