Libyan pro-government forces targeted the Islamic State group in Sirte with a wave of air strikes Thursday to help pave the way for ground troops to take the jihadists' coastal stronghold.

"Our air force today launched an intense series of air strikes that targeted various (IS) positions in Sirte," Reda Issa, a spokesman for Libya's Government of National Unity (GNA), told AFP.

"Military engineering teams are working to clear mines and bombs planted by (IS) to open the way for our ground forces to continue their advance on different parts of the city," he said.

The fall of Sirte would be a major blow to IS, which has faced a series of setbacks in Syria and Iraq.

Until early May, the extremist group controlled a 280 kilometre (170 mile) stretch of Mediterranean coastline around Sirte.

Since May 12, pro-government forces from the west, Libyan naval forces and eastern militias have pushed the jihadists back into a residential zone of just five square kilometres (two square miles).

But their early advances slowed when they entered Sirte on June 9 and reached built-up central and northern parts of the city. IS hit back with suicide car bombs and sniper fire.

IS announced on social media Thursday that its fighters had detonated two bombs near a group of pro-government fighters in the east of the city, burned a tank and hit a reconnaissance aircraft.

Tuesday was the bloodiest day in the operation so far for pro-government forces, who lost 36 dead and over 100 injured.

The GNA's health ministry on Wednesday appealed to Libyan doctors outside the country to return to the country and help treat "those injured in the war being fought by the sons of the nation".

Since the start of the offensive, nearly 200 members of the pro-GNA forces have been killed and over 600 injured, according to medical sources. The jihadists' losses are not known.

Pro-government forces, commanded out of Misrata, 190 kilometres (120 miles) to the northwest, are primarily made up of western militias that were born during the 2011 rebellion that overthrew dictator Moamer Kadhafi.

A militia set up to guard the country's main oil installations has also been advancing on IS from the east.