Turkey's armed forces on Wednesday launched new artillery strikes on jihadist positions in Syria, after three days of deadly fire on a Turkish border town that has left residents on edge.

Kilis, which lies just a few kilometres from the border with Syria, has been hit by fire from Katyusha-type rockets every day this week raising concerns over its vulnerability. 

Two people were killed by shelling from an area controlled by Islamic State (IS) jihadists on Tuesday and four more rockets hit the town on Wednesday but caused no injuries, a Turkish official said.

Speaking in Ankara, Prime Minister Ahmet Davutoglu confirmed Turkish troops had hit IS positions in Syria. 

In a sign of Ankara's alarm over the repeated firing on Kilis, Defence Minister Ismet Yilmaz, powerful intelligence chief Hakan Fidan and top general Hulusi Akar visited the town on Wednesday to investigate the situation.

Addressing a press conference there, Yilmaz confirmed Turkish artillery hit areas controlled by IS and warned against any further attacks on Turkey.

"If they harm Turkey, they will be subjected to much more," Yilmaz said. "Whoever is friendly with Turkey will find it is to their benefit."

Yilmaz also said the government had established a commission to compensate residents for their losses. 

 A town of refugees

 In Ankara, Davutoglu also warned that those who attacked Turkey would pay "the heaviest price", insisting that the government was determined to protect its citizens from the latest cycle of violence. 

Dozens of people had rallied in the centre of Kilis on Tuesday to demand protection from the shelling, Turkish media reports said.

The violence comes after IS militants wrested back control of the town of Al-Rai near the Turkish border, which rival rebels had captured last week. 

Kilis, a town of just under 100,000, is the only major urban centre in Turkey which now has a majority of Syrians after the influx of refugees from the civil war.

Neither the Al-Qaeda-affiliated Al-Nusra Front nor IS are included in a truce brokered by the United States and Russia that came into force on February 27.

Washington has applauded Turkey's role in the anti-IS coalition but US officials on occasion have urged Ankara to do more.

In a separate development, Turkey's army opened fire on a group of four people -- one man and three women -- who attempted to cross into the border town of Karkamis late Tuesday from IS-held Jarablus in Syria, local media reported.

The man, a Turk, was injured and later died in hospital and the women -- one Turk and two Moroccans -- were detained on suspicion of being IS members, the Dogan news agency reported.

The women were to be brought to court on charges of "membership in an armed terrorist organisation" and "violation of a special security region," it added.

In a separate development, a spokesman for Angela Merkel said the German chancellor was not planning to travel to Turkey this week to inaugurate a new Syrian refugee centre, contradicting a previous announcement by Ankara.

The announcement comes as diplomatic tensions soared between Berlin and Ankara over a vulgar satirical poem by German TV comic.