Hundreds of pro-regime troops have been killed in Aleppo and Deir Az Zor provinces as opposition armed groups and regime forces fight over control of several areas, according to sources.

At least 170 pro-regime troops have been killed in clashes that occurred in Khan Touman and Deir Az-Zor city, the UK-based Syrian Observatory for Human Rights (SOHR) said on Saturday.

The developments come as John Kerry, the US secretary of state, is in Saudi Arabia where he is meeting King Salman bin Abdulaziz Al Saud and the country's foreign minister.

Kerry has embarked on an ambitious week of negotiations to push for ‘international cooperation’ to end the fighting in Syria.

He will head to Vienna, Austria, later to make his case with European leaders.

Elsewhere in Syria, regime air strikes have killed at least 12 people and left several injured in Idlib city, among them children, the SOHR said on Sunday.

PHOTO CAPTION

Residents inspect a site damaged by a regime or Russian airstrike in Hafsarja, in Idlib province, Syria May 9, 2016.

Al-Jazeera