Istanbul, Turkey (CNN) Seven Turkish soldiers and one civilian personnel were killed in Syria on Sunday, Turkey's first fatalities as a result of direct confrontation between the countries since the start of Syria's civil war in 2011.

The Turkish Defense Ministry released the latest death toll on Tuesday. Several other troops had been also wounded in northwest Syria's Idlib province after they came under heavy artillery fire from the Syrian government, according to an earlier statement from the ministry, which specified that the troops were reinforcements.

On Monday, Turkish President Recep Tayyip Erdogan said up to 35 Syrian government soldiers had responded and pledged further retaliation.

Erdogan said up to 40 Syrian targets were being considered as part of the operation, and warned Russia -- the most powerful backer of Syrian President Bashar al-Assad -- to "not stand in our way."

"We told the Russian authorities you are not party to this it is totally the regime and do not stand in our way. Because we have martyrs, we cannot remain silent. We will continue to respond, including with our F-16s, our howitzers, our artillery, it is all in the field firing on the targets determined by our national intelligence," Erdogan said.

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