Kuwait City (AFP) - Thousands of Kuwaitis braved scorching summer heat on Saturday to attend the funerals of 18 out of 26 victims of a Shiite mosque bombing claimed by the Islamic State group.

The bodies of the remaining eight victims were flown to Iraq's Shiite holy city of Najaf for burial, State Minister for Cabinet Affairs Sheikh Mohammad Abdullah Al-Sabah said.

Draped in Kuwaiti flags, the bodies were borne by mourners chanting religious slogans.

Mourners turned out in large numbers despite the Ramadan daylight fast and as temperatures hit 45 degrees Celsius (113 Fahrenheit).

"This crowd is the proof that the objectives of the criminal act have failed," parliament speaker Marzouk al-Ghanem told reporters.

The mourners, who included women clad in black Islamic dress, carried Kuwaiti flags and black and green banners bearing religious slogans.

The attack targeted Al-Imam Al-Sadeq mosque in the capital Kuwait City during Friday noon prayers.

The interior ministry said in a statement that 26 people and the IS suicide bomber were killed and 227 wounded in one of the country's worst bombings and its first ever on a mosque.

The health ministry said that 40 wounded are still in hospital.