It was not clear whether Moscow would use its influence with Assad to advance Annan's six-point peace plan, which includes demands for a ceasefire, the immediate withdrawal of heavy armour from residential areas and access for humanitarian aid. "Syria has an opportunity today to work with me and this mediation process to put an end to the conflict, to the fighting, allow access to those in need of humanitarian assistance as well as embark on a political process that will lead to a peaceful settlement," Annan said after the talks.In the Korean capital Seoul, Obama and Erdogan discussed providing medical supplies and communications support to the Syrian opposition but there was no talk of providing lethal aid for rebel forces."We worked on a common agenda in terms of how we can support both humanitarian efforts ... (and) the efforts of Kofi Annan to bring about much needed change (in Syria)," Obama said after his meeting with Erdogan, a sharp critic of Assad.Human shields and heavy shelling New York-based Human Rights Watch published videos, obtained from opposition activists, in which people in civilian clothes walk in front of several armed soldiers and infantry fighting vehicles. Activists say the army had compelled the men to walk in front to protect the soldiers.The statement said that residents reported government forces placing children on tanks and inside security buses. "The Syrian army's use of human shields is yet another reason why the UN Security Council should refer Syria to the International Criminal Court," said Ole Solvang, a HRW emergencies researcher.It was impossible to verify reports independently because Syrian authorities have prevented foreign journalists and human rights workers from entering affected areas.Waleed al-Faris, an opposition activist from Homs, told Reuters that Sunday's shelling, using tank and mortar fire, was the worst he had seen."There are ten dead and hundreds wounded," he said. "I have not experienced shelling this heavy since Baba Amr."In the southern province of Deraa, birthplace of the revolt, government forces and rebels clashed on Sunday."Thousands of soldiers and over a hundred military vehicles are attempting to enter the area of Lahat in Deraa province today, but they are clashing with rebels," said Rami Abdelrahman, head of the Syrian Observatory for Human Rights, adding that at least five soldiers and three rebels had been killed.The Syrian state news agency SANA said six "terrorists" had been killed on during dawn raid on a hideout in Deraa.The SOHR said 27 were killed around Syria on Sunday, 15 of them civilians, during heavy shelling in the central city of Homs and northwestern province of Idlib.In the eastern city of Deir al-Zor, Syrian troops conducted house-to-house raids in search of dissidents, SOHR said.