Russian and Iranian-backed regime forces now control around 60 percent of Syrian territory The Observatory said Friday"s shelling had caused the highest civilian toll since the de-escalation deal, reached almost a year ago BEIRUT: Syrian regime shelling on an opposition-held southern region has killed at least six civilians, hours after US warning not to jeopardize talks on the area"s fate, a monitoring group said Friday. The Syrian Observatory for Human Rights said the casualties, who included two children, were killed in shelling on two villages in the north of Daraa province. The Britain-based monitor, which relies on a large network of sources inside Syria, said the shelling came from army positions that had recently received reinforcements. The US State Department had on Thursday warned Damascus against any military action that could scupper ongoing talks aimed at finding a settlement for the complex southern front. “We reiterate that any Syrian government military actions against the southwest de-escalation zone risk broadening the conflict,” spokeswoman Heather Nauert said in a statement. “We affirm again that the United States will take firm and appropriate measures in response to Syrian government violations in this area.” The United States, Russia and Jordan agreed to a de-escalation deal in the southern province, and negotiations are continuing in a bid to reach a deal that would remove the need for a government offensive. The Observatory said Friday"s shelling had caused the highest civilian toll since the de-escalation deal, reached almost a year ago. The region borders Jordan and the Israeli-annexed Golan Heights. Rebel groups, who still control about two thirds of Daraa, have so far refused to negotiate with the Syrian regime. In an interview with Iran"s Al-Alam television channel earlier this week, Syrian President Bashar Assad said contacts were ongoing between Russia, the US and Israel over the southern front. “We are giving the political talks a chance, but if they fail, there will be no choice but liberation by force,” he said. The regime wants rebels to withdraw from the area either by force or under a deal. Also at stake in the current talks are the future of a US military base in southeastern Syria and the presence of Iranian and allied forces in southern parts of Syria near the border with Israel. Meanwhile, Assad attended a mosque in the country"s west on Friday for prayers marking the end of Ramadan, in a rare appearance outside Damascus, images on his social media showed. “President Assad performs the Eid Al-Fitr prayer at the Sayyida Khadija Mosque in the city of Tartus,” a caption read. In one picture, he was seen praying alongside the country"s top Muslim cleric and its Islamic endowments minister. Another image showed him surrounded by dozens of worshippers who appeared to be offering him Eid greetings. Assad has rarely appeared in public outside Damascus since Syria"s conflict broke out more than six years ago. The coastal city of Tartus is the site of a naval base belonging to Assad"s key backer Russia, which has helped his forces retake swathes of opposition-held territory. Like neighboring Latakia province, from which Assad"s clan hails, Tartus is a stronghold of his Alawite sect. The region has largely escaped the destruction that has blighted other areas of Syria but it has suffered a heavy human toll from military service in the conflict that has killed 350,000 people since 2011. Russian and Iranian-backed regime forces now control around 60 percent of Syrian territory.