Earlier, Taliban sources said group's leadership had arrived in Islamabad for talks

Afghan govt confirms the death of the elusive leader

Afghan government statement also confirms Omar's death, says grounds for peace talks are now more paved than before

Official says some headway is expected in the July 31 negotiations

Afghan peace body spokesperson says exact venue of talks still undecided

Doha-based Taliban leaders said to have broad-based backing on the peace talks

Afghanistan claims four people were killed in cross-border firing

Afghan foreign ministry alleges three civilians were killed in Pakistan's cross-border shelling

Analysis posted on group's website suggests four points to making the peace process successful

Tehreek-e-Taliban Pakistan claimed responsibility for the attack