ISIL claims responsibility for blast targeting Shia Muslims returning from Arbaeen pilgrimage in city of Karbala.

An earlier version of this story stated that the death toll had surpassed 100. Our sources in Iraq now say the toll is 97.

Nearly 100 people have been killed and dozens wounded in a massive suicide truck bomb blast at a petrol station south of Iraq’s capital Baghdad, according to police and medical sources.

The target of Thursday’s attack near the town of Hilla appeared to be Shia Muslim pilgrims returning from the annual Arbaeen pilgrimage in the holy city of Karbala.

READ MORE: ISIL suicide bombers kill dozens in two cities

The Islamic State of Iraq and the Levant (ISIL) group claimed responsibility for the attack.

Al Jazeera’s Hoda Abdel-Hamid, reporting from Erbil, said an oil tanker rigged with explosives tore through the petrol station, which has a restaurant on its premises that is popular with travellers.

“The whole place was completely wrecked. It was a massive blast,” Abdel-Hamid said.

“When the gas tanker blew up, it also torched several buses and minivans that were carrying the pilgrims.”

Our correspondent said that as of 03:00 GMT on Friday the number of those killed in the attack was at least 97, rising from a previous death toll of 80.

Earlier, security sources had said they expected casualty figures to increase in the coming hours.

“It is believed that among them are not only Iraqis, but some Iranians too, while some unconfirmed reports also say that there could be some Bahrainis among the victims.”

“With today’s attack, ISIL is sending the message that it can still cause and inflict a lot of pain,” Abdel-Hamid said.

READ MORE: Iraqi militiamen sever ISIL’s key supply line to Syria

Videos circulating on social media showed debris scattered over a large area along the main highway linking Baghdad to the main southern port city of Basra.

“There are completely charred corpses at the scene,” said Falah al-Radhi, head of the provincial security committee, adding that at least 20 wounded were transferred to nearby hospitals.

The Joint Operations Command in Baghdad issued a statement saying the lorry was packed with 500 litres of ammonium nitrate, a chemical compound used in many explosive devices.

ISIL has intensified attacks over the past month in areas out of its control in efforts to weaken a large-scale military offensive launched last month to retake Mosul, the last major city under its control in Iraq.

The latest attack “highlights just how difficult it is to guarantee any kind of security in certain areas of Iraq”, Al Jazeera’s Charles Stratford, reporting from Dohuk in northern Iraq, said.

“Despite of evidence of ISIL getting hit very hard, they still seem to be able to attack when and where they want in certain parts of the country.”

The International Organization for Migration said on Thursday that around 76,000 people had been displaced since the start of the Mosul offensive on October 17.

The group said that about 7,000 people had already returned to their homes, leaving roughly 69,000 still displaced, most of them in camps.