The new UN human rights chief urged world powers on Monday to protect women and minorities targeted by Islamic State militants in Iraq and Syria, saying the fighters were trying to create a "house of blood".

Jordan's Zeid Ra'ad Al Hussein, the first Muslim to hold the position, called for the international community to focus on ending the "increasingly conjoined" conflict in the two countries, and abuses in other hotspots from Ukraine to Gaza.

Islamic State's Sunni Muslim fighters have over-run large parts of Syria and Iraq since June, declaring a cross-border caliphate. The Geneva-based UN Human Rights Council last week agreed to send a team to investigate killings and other abuses carried out by the group on "an unimaginable scale".

Zeid, Jordan's former UN ambassador and a Jordanian prince, described Islamic State in his maiden speech to the council as "takfiris" - hardline Sunni militants who justify killing others by branding them apostates.

"Do they believe they are acting courageously? Barbarically slaughtering captives? ... They reveal only what a Takfiri state would look like, should this movement actually try to govern in the future," said Zeid, who succeeds Navi Pillay in the Geneva hotseat.

"It would be a harsh, mean-spirited, house of blood, where no shade would be offered, nor shelter given, to any non-Takfiri in their midst," Zeid added.

He called on Iraq's new government and prime minister to consider joining the International Criminal Court (ICC) to ensure accountability for crimes committed there.

"In particular, dedicated efforts are urgently needed to protect religious and ethnic groups, children - who are at risk of forcible recruitment and sexual violence - and women, who have been the targets of severe restrictions," Zeid said.

The ambassadors of Iraq and Syria, in separate speeches, called for combating "terrorist groups" in their homelands and for halting the flow of weapons and funds to Islamist militants.

"Terrorists must not be armed, the source of financing must be stopped. Infiltration of terrorists from abroad must be stopped," said Syria's new envoy Hussam Edin Aala. - Reuters