Isis militants claim to have killed at least 100 people, including children, with a car bomb in the Iraqi town of Khan Bani Saad, where people had gathered to celebrate Eid al-Fitr.

In one of the deadliest attacks since Isis extremists seized large swathes of the country, several buildings were brought to the ground.

A number of people who had gathered together to mark the end of the holy month of Ramadan were crushed in the collapse, according to police officers and medics.

Police major Ahmed al-Tamimi described the scene as “devastating”.

“Some people were using vegetable boxes to collect children's body parts,” he said.

Isis tweeted in a statement that the attack was to avenge the killing of Sunni Muslims in the northern Iraqi town of Hawija, and that the suicide car bomber was carrying around three tonnes of explosives.

The group said the attack in the province of Diyala, which is not its first, was aimed at "rejectionists" - the derogatory term the group uses to refer to Shia Muslims.

Crowds consumed by grief and anger over the attack smashed the windows of cars parked in the street.

It is feared the death toll could yet climb, as rescue teams worked to retrieve the remains of the victims from under the rubble, an officer from the Diyala police command told Reuters.

Ramadan is an important time of celebration for Muslims, and marks the end of a month of fasting.

In pictures: Ramadan around the world Show all 27 1 /27 In pictures: Ramadan around the world In pictures: Ramadan around the world In pictures: Ramadan around the world In pictures: Ramadan around the world Russia Russian Muslims pray outside the central mosque in Moscow, during celebrations of Eid al-Fitr marking the end of the fasting month of Ramadan AFP/Getty Images In pictures: Ramadan around the world Turkey Turkish Muslims offer Eid al Fitr prayers as they mark the first day of the Eid al-Fitr at Fatih Sultan Mosque in Istanbul Getty Images In pictures: Ramadan around the world Syria A Syrian Dervish dances as part of a traditional event organised by the Syrian Ministry of Tourism under the title 'Music and Dervishes' in the old city of Damascus EPA In pictures: Ramadan around the world Bosnia and Herzegovina A Bosnian Muslim man, wearing a traditional Bosnian outfit, fires a canon from a vantage point overlooking Sarajevo to mark the end of daily fasting on the final day of the Islamic holy month of Ramadan AFP/Getty Images In pictures: Ramadan around the world Pakistan A general view of an illuminated Mosque as Muslims pray during the 27th night of Ramadan, in Peshawar EPA In pictures: Ramadan around the world Pakistan Muslim women offer prayer of the Jumat-ul-wida, the last Friday of the Islamic holy month of Ramadan at a mosque in Lahore AP In pictures: Ramadan around the world India Muslims offer prayers on the last Friday of the holy month of Ramadan in Dargah Khwaja Moinuddin Chisti Rex Features In pictures: Ramadan around the world Saudi Arabia The Prophet Mohammed Mosque in the holy city of Medina, during Ramadan EPA In pictures: Ramadan around the world Malaysia A Malaysian swings around fireworks to celebrate the last day of the Muslims' Holy fasting month of Ramadan, in Shah Alam, outside Kuala Lumpur In pictures: Ramadan around the world Kyrgyzstan Kyrgyz Muslims pray during the Eid al-Fitr Muslim celebration marking the end of Ramadan in Bishkek EPA In pictures: Ramadan around the world Ivory Coast People pray during the Laylat Al Qadr prayers on the 27th day of the Islamic month of fasting, Ramadan in the front of the Aghin mosque in Abidjan AFP/Getty Images In pictures: Ramadan around the world Syria Syrians shop for traditional sweets in Kafr Batna in the rebel-held Eastern Ghouta area, on the outskirts of the capital Damascus, ahead of Eid al-Fitr which marks the end of the Muslim holy month of Ramadan AFP/Getty Images In pictures: Ramadan around the world Israel A Palestinian woman prays on the third Friday of the holy fasting month of Ramadan on the compound known to Muslims as Noble Sanctuary and to Jews as Temple Mount in Jerusalem's Old City REUTERS In pictures: Ramadan around the world Iran Iranian Shiite Muslims pray at the graves of soldiers who were killed during 1980-88 Iran-Iraq War, at the Behesht-e-Zahra cemetery, during the holy fasting month of Ramadan, just outside Tehran, Iran AP In pictures: Ramadan around the world Israel A Palestinian man pours water on Muslim worshippers' heads to cool off in the heat, as others pray outside the Dome of the Rock at the al-Aqsa Mosque in Jerusalem during the last Friday prayers of the Muslim holy month of Ramadan EPA In pictures: Ramadan around the world Afghanistan Afghan women wait to receive food ration during the Muslim holy month of Ramadan in Herat EPA In pictures: Ramadan around the world Pakistan A Pakistani Muslim reads the holy Koran as he observes Itikaf at a Mosque, in Peshawar EPA In pictures: Ramadan around the world India Kashmiri Muslim women offer prayers as the head priest (not pictured) displays a holy relic believed to be hair from the beard of the Prophet Mohammed, during special prayers to observe the Martyr Day of Hazrat Ali, cousin of Prophet Mohammed, on the 21st day of Ramadan, at the Hazratbal Shrine in Srinagar, the summer capital of Indian Kashmir EPA In pictures: Ramadan around the world India Indian Muslims sit with bowls of porridge(Nombu kanji)as they prepare to break the fast with the Iftar meal during the Islamic month of Ramadan at The Wallajah Big Mosque in Chennai AFP/Getty Images In pictures: Ramadan around the world Lebanon Spectators watch fireworks as a giant Fanous, or Ramadan lantern, is switched on four days before the start of Ramadan month in front of Mohamed al-Amine Mosque in downtown Beirut EPA In pictures: Ramadan around the world Lebanon Lebanese children perform during activities celebrating the upcoming Muslim holy month of Ramadan, in downtown Beirut AP In pictures: Ramadan around the world Palestine Palestinian men drink tea on the promenade of Gaza beach Getty In pictures: Ramadan around the world Indonesia Members of Nahdlatul Ulama, the biggest Muslim organisation in Indonesia, hold a mass prayer session to welcome in Ramadan in Jakarta AFP/Getty In pictures: Ramadan around the world Iraq Iraqis shop for food in a preparation for the Muslim holy month of Ramadan in Baghdad AP In pictures: Ramadan around the world Indonesia Foods is seen during 'Unggah-unggahan' ceremony to welcome in the Muslim fasting month of Ramadan in Pekuncen village Getty

The occasion sees families and loved ones wear their best clothes and gather to give thanks and to eat their first daylight meal in a month.

However, Diyala provincial government declared three days' mourning and ordered all parks and entertainment places to close for the rest of the Eid ul-Fitr holiday to avoid further attacks.