The Guardian reports: Evidence gathered by UN investigators in Syria shows human rights violations, including executions “on an alarming scale”, according to a new report on a conflict that is spiralling into “deeper and more destructive violence” and in which sectarian motives now predominate.

Against a background of escalating bloodshed and global concern, with gunmen killing seven on Wednesday at a pro-regime TV station near Damascus, the foreign ministers of the world’s leading powers have been invited to meet in Geneva on Saturday in a desperate attempt to agree a political exit from the impasse.

On Tuesday, president Bashar al-Assad ratcheted up his own language by describing the crisis as “a real war” and pledged to do everything necessary to prevail. Assad had previously always blamed the uprising on “armed terrorist gangs” backed by the west and Arab countries.

Underlining the gravity of the situation, the Syrian Observatory for Human Rights described the last week as the bloodiest yet in the 16-month uprising. Observatory director Rami Abdul-Rahman said 916 people had been killed from 20 to 26 June. On Tuesday alone the reported death toll was 113, though these figures cannot be independently verified. Tank fire was reported from al-Qusair near Homs. Other attacks by government forces were reported on Wednesday in Deraa and Zamalka.