(Adds Cavusoglu comments, background)
By Daren Butler
ISTANBUL, June 16 (Reuters) - A Turkish observation post in Syria's Idlib region was attacked with mortar fire and shelling from an area controlled by Syrian government forces, causing damage but no casualties, the Turkish Defence Ministry said on Sunday.
The ministry said its forces immediately retaliated with heavy weapons and it made representations to Moscow over the incident, the second attack of its kind within a week.
"It is impossible for us to tolerate the regime's harassment targeting our soldiers. We will put them in their place," Turkish Foreign Minister Mevlut Cavusoglu said in a televised speech in the southern Turkish province of Hatay, bordering Syria.
The ministry did not specify when the shelling occurred, but said the attack was launched from what it named the Tall Bazan area and it was assessed to be deliberate.
Russia, which supports Syrian President Bashar al-Assad in his country's civil war, and Turkey, long a backer of rebels, co-sponsored a de-escalation agreement for the area that has been in place since last year.
But the deal has faltered in recent months, forcing hundreds of thousands of civilians to flee. Idlib is the last remaining bastion for anti-government rebels after eight years of civil war.
Cavusoglu said the latest "aggression" was contrary to the Idlib agreement which Turkey signed with Russia.
"It is the responsibility of Iran and Russia, with which we have worked in close cooperation on Syria, to halt the regime," he added.
On Thursday Russia and Syria gave sharply conflicting accounts of a previous attack on a different Turkish outpost.
Turkey blamed Syrian government forces for that earlier attack but Moscow said it was carried out by Assad's rebel enemies. Russia said on Wednesday that a full ceasefire had been put in place in the area, but Turkey denied this.
The latest incidents highlighted the erosion of the de-escalation deal, agreed last year to shield Idlib from a government assault.
The region is home to hundreds of thousands of people who fled other parts of Syria as government forces advanced through the country since Moscow joined the war on the side of Assad in 2015, tipping the conflict in his favour.
Since April, government forces have increased their shelling and bombing of the area, killing scores of people.
The rebels say the government action is part of a campaign for an assault that would breach the de-escalation agreement. The government and its Russian allies say the action is in response to rebel violations, including the presence of fighters in a demilitarised zone. (Reporting by Daren Butler Editing by Andrew Heavens and Jane Merriman)