Eritrea planned a major bomb attack on the African Union summit in Ethiopia at the start of this year which the attackers intended would "make Addis Ababa like Baghdad", according to a report from the United Nations.

The report, compiled by a U.N. monitoring group and seen by Reuters, also claims Eritrea funded Somalia's Al Qaeda-linked rebel group Al Shabaab.

Al Shabaab has warned international aid agencies against providing humanitarian assistance in Somalia, where millions of people are affected by a major drought and food crisis. The World Food Program says it cannot reach around 2.2 million people in urgent need of aid, due to Al Shabaab's threats of violence.

Conservative estimates from the U.N. group suggest the rebels may be earning as much as $100 million a year through smuggling, extortion and "jihad contributions". 

Thirty African leaders attended the January summit in the Ethiopian capital. The U.N. report says that Eritrean intelligence services planned a car bomb attack on the AU's headquarters in Addis Ababa during that meeting, as well as parallel attacks on the Ethiopian prime minister's office, the hotel were the leaders were staying and an open-air market.

The attack would "almost certainly" have caused a high number of civilian deaths and had a serious impact on Ethiopia's economy, the Guardian quotes the report. Ethiopian security forces succeeded in foiling the bomb plot.

Over the last two decades, relations between Ethiopian and Eritrean leaders have seriously soured from the time when they served as allies during their struggles to gain independence. 

The report also claims that two companies, one registered in Hong Kong and the other in Lebanon, violated the international arms embargo on Somalia during the group's monitoring period.