Pope Benedict on Monday asked Iraq's Catholics to work for peace in honour of the memory of a Chaldean Catholic archbishop who was kidnapped by gunmen and found dead last week.

The death of Paulos Faraj Rahho, the Archbishop of Mosul, was the most-high profile attack on Iraq's Christians since the U.S.-led invasion in 2003. Iraqi Prime Minister Nuri al-Maliki has blamed al Qaeda.

"We have cried over his death, the inhumane way in which he had to end his life on Earth," the Pope said during a mass at the Vatican in Rahho's memory.

"But today ... we want to thank God for all of the good that he did (and) that his Christians know to continue in their effort to build a peaceful society."

Rahho was abducted on February 29 after gunmen attacked his car and killed his driver and two guards. His body was found in a shallow grave in eastern Mosul on Thursday. It was not clear how Rahho, who was known to suffer poor health, had died.

Police at the Mosul morgue said he appeared to have been dead a week and his body bore no bullet wounds.

On Sunday, the Pope forcefully called for an end to Iraq's violence, saying: "Enough with the massacres, enough with the violence, enough with hatred in Iraq!".

Chaldeans belong to a branch of the Roman Catholic Church that practices an ancient Eastern rite and form the biggest Christian community in mostly Muslim Iraq, although tens of thousands are reported to have fled Iraq.