(Adds quotes from residents)
BAGHDAD, June 11 (Reuters) - Militants from an al Qaeda splinter group who seized Iraq's second biggest city of Mosul this week have advanced into the oil refinery town of Baiji, setting the court house and police station on fire, security sources said on Wednesday.
They said around 250 guards at the refinery had agreed to withdraw to another town after the militants sent a delegation of local tribal chiefs to persuade them to pull out.
Baiji resident Jasim al-Qaisi, said the militants also warned local police and soldiers not to challenge them.
"Yesterday at sunset some gunmen contacted the most prominent tribal sheikhs in Baiji via cellphone and told them: 'We are coming to die or control Baiji, so we advise you to ask your sons in the police and army to lay down their weapons and withdraw before (Tuesday) evening prayer'."
Militants entered Baiji later on Tuesday evening in around 60 vehicles, releasing prisoners in the town.
Baiji refinery is Iraq's biggest, supplying oil products to most of the country's provinces. A worker there said the morning shift had not been allowed to take over and the night shift was still working.
The push into Baiji followed the capture on Tuesday of Mosul by militants from the Islamic State in Iraq and the Levant (ISIL) - an offshoot of al Qaeda - which has also seized territory in neighbouring Syria.
(Reporting by Raheem Salman in Baghdad and Ghazwan Hassan in Tikrit; writing by Dominic Evans and Editing by Samia Nakhoul)