The Turkish military retaliated with artillery fire for a sixth straight day Monday after a Syrian shell hit its territory, and Turkey's president warned that "the worst-case scenario we have all been dreading" is unfolding in Syria and along its borders.

Turkish President Abdullah Gul called on the international community to do more to try to end Syria's nearly 19-month-old conflict, which has claimed more than 30,000 lives and — with Turkey-Syria tensions rising — heightened fears of a regional conflagration.

U.N. chief Ban Ki-moon on Monday warned that the escalating conflict on the Syrian-Turkish border is "extremely dangerous."

The main Syrian opposition group, meanwhile, signalled it is softening its position on possible talks to arrange a political transition.

In the past, the Syrian National Council has said that President Bashar al-Assad and his inner circle must step down before such talks can begin. However, the SNC chief said Monday that talks would be possible with members of the regime who do not have blood on their hands.

In the latest cross-border incident, a Syrian artillery shell fell on Turkey's border province of Hatay on Monday, the provincial governor's office said. The state-run Anadolu news agency said the round landed in a cotton field near the town of Altinozu. People were working in the field but no one was injured, Anadolu said.

Turkey retaliates

Turkey retaliated Monday, as it did on five previous days, the governor's office said. Last week, after deadly cross-border shelling, Ankara warned Assad that it will respond to each shell or mortar round that hits Turkish soil.

Turkey also sent more artillery to hotspots along the troubled border on Monday, Turkish media reported.

The persistent Syrian shelling suggests the cross-border fire of recent days is not accidental. Turkey, along with other foreign allies of the Syrian opposition, is reluctant to intervene militarily in Syria, and Damascus' military strategy relies, in part, on the high threshold for foreign intervention.

Gul, the Turkish president, described Syria's civil war and its regional impact as the "worst-case scenario that we've all been dreading," adding that along with the suffering of the Syrian people, "once in a while we're also affected."

Speaking to reporters in Ankara, Gul also said the situation in Syria must not be allowed to continue.

"Sooner rather than later there will be change, a transition," he said. "Our only hope is that this happens before more blood is shed, and before Syria self-destructs more than it already has. It's also crucial that the international community act in a more effective way."

Peace efforts fail

Efforts to get the two sides to negotiate a peaceful transition have failed up to now.

Activists reported violence in different parts of the country, mostly in the central city of Homs, the northern city of Aleppo, and the southern region of Daraa.

The Syrian Observatory for Human Rights, a Britain-based activist group, said 20 people were killed in the southern village of Karak, which has been attacked by government troops. It said the 20 were killed when vehicles transporting wounded people were targeted by troops.

Meanwhile, residents of the Turkish border town of Akcakale, struck repeatedly by shelling from Syria, said they fear for their safety, even though Turkish troops have deployed to the area.

"If this shelling is going to continue day in and day out, we can't live here. We are not safe, our property is not safe," said Hamit Ciftcioglu, whose jewelry store is just 75 metres from where a mortar round hit Sunday.

Last week, officials decided to re-open schools that had been closed for weeks due to dangerous conditions. But children who lined up Monday morning found they had nowhere to go.

"They told us schools would reopen on Monday. So we sent our children to schools this morning but unfortunately they had to come back. They told us the schools were still closed," said Isa Tokdemir, a father of two.