"The UN's humanitarian chief Jan Egeland said a fraction of the funds needed to feed the refugees had been raised.
He said Chad's refugee crisis had been "overshadowed" by events in Darfur.
The Darfur conflict has killed some 200,000 people and created 2m refugees. Many have fled to Chad, to be joined by Chadians fleeing internal unrest.
Touring refugee camps in eastern Chad, near the border with Sudan, Mr Egeland told the Reuters news agency the security situation in the region had descended into "total chaos".
Aid agencies estimate they need $180m to feed the refugees in eastern Chad.
"Only 16% of the humanitarian funds required to feed these people has been met so far," Mr Egeland is quoted as saying" Read in full here
"The U.N. refugee agency on Friday said it is "very disturbed by reports of ongoing infiltration of armed Sudanese rebels inside and near some refugee camps in eastern Chad and fear further recruitment of refugees for military activities."
"We strongly condemn the infiltration of refugee camps by any military presence. This situation is totally unacceptable. It violates the civilian and humanitarian character of the refugee camps and risks making refugees and humanitarian workers a target.""
"Describing the latest reports of refugee camp infiltration, UNHCR said "men identified as belonging to a Sudanese rebel armed movement were spotted earlier this week in the northern Oure Cassoni camp" near the Sudanese border.
"The camp, which shelters some 27,000 Sudanese refugees from Darfur, has been suspected of being used as a rest and recuperation base for Sudanese rebels. This is the first time however, that rebels have been seen so openly in broad daylight, in vehicles and walking around the camp," the UNHCR said in a statement.
"We immediately informed the local authorities about the infiltration. On Wednesday and Thursday we met with our implementing partners, local authorities, camp gendarmes and refugee leaders. The refugees were clearly reminded of their rights, duties and obligation not to engage in political nor military activity in Chad and most specifically not in the camps."
The agency urged authorities in Chad, rebel groups and refugees "that infiltration of the camps cannot continue. If not stopped, it could result in the suspension of humanitarian activities.""
Read more here
Same day as the report just mentioned, Human Rights Watch released a briefing
on the situation in Chad.
"Witnesses showed Human Rights Watch researchers one of the massacre sites in four adjacent villages approximately 70 kilometers west of the Sudan border, and confirmed that a total of 118 people were killed on April 12 and 13, a period when Chadian rebel groups based in Darfur were pursuing a westward offensive on the Chadian capital, N’djamena" Footage is available on the HRW link above.
"Survivors described unarmed villagers being surrounded and then gunned down or hacked to death with machetes by militiamen wearing blue Sudanese military fatigues and turbans. Witnesses described their attackers as Janjaweed and noted that Chadians who had recently migrated to Sudan were among them. The recent militia attacks in Chad seem to be part of a wider pattern of cross-border violence that Human Rights Watch has documented over the past year, during which time the Sudanese state of West Darfur, which borders Chad for more than 500 kilometers, has become increasingly volatile. More than a dozen armed groups, including four factions of the Darfur rebel movements, several Sudanese government-backed militias, and Chadian rebel groups are active along the porous border. Livestock raiding has become common, but the April attacks on the four Chadian villages were unusual for the high number of deaths. "