SIRTE, Libya – Violent clashes erupted between Islamic State-affiliated militants and militias aligned with the Islamist self-declared government near Sirte in north-central Libya.

After surrounding the Islamic State-controlled city of Sirte for several weeks, the militias were about 16 kilometres (10 miles) west of the centre of the city on Sunday. Other militias fighting their way into Sirte from the east are only 3 kilometres (1.8 miles) from the centre.

The Tripoli government has previously denied the existence of the Islamic State affiliate. The militias backing the Tripoli government, which is not elected or internationally recognized, are also largely Islamist. The more-extremist Islamic State group has taken control of at least two cities, Sirte and Darna.

An official from Battalion 166, a unit fighting in Sirte, said five of his men had been killed and more than 17 wounded over the past two days. He spoke on condition of anonymity because he was not authorized to speak to journalists.

Field commander Mohammed Abdullah said that the fighting started when an Islamic State-affiliated suicide car bomber killed a solider from Battalion 166.

Abdullah said they were trying to contain the crisis. He called for the Islamic State affiliate to surrender their weapons and issue a statement acknowledging the legitimacy of the state.

He said that they have information that the Islamic State affiliate has taken over a hotel, the main conference centre and a prison inside Sirte.

The Libyan turmoil has provided fertile ground for militants allied with the Islamic State group, which is fighting in Iraq and Syria to expand its self-styled caliphate.

These IS-affiliated militants carried out a deadly attack on a luxury hotel in Tripoli in January, and in February released a video showing them beheading 21 Egyptian Christians. The Egyptian military launched airstrikes on Darna in retaliation.

Libya has collapsed into chaos following the ouster of longtime autocrat Moammar Gadhafi in 2011. Two rival governments and parliaments — each backed by different militias — rule opposite sides of the country.