Jan Egeland said violence in Darfur had become so bad that the UN operation could “all end tomorrow – it’s as serious as that”.
Mr Egeland said that international aid workers were increasingly being targeted by armed groups.
At least 36 people were killed in eastern Chad after gunmen on horseback – said to have crossed the border from Darfur – raided the village of Madayouna in an apparent attempt to steal cattle.
The military killed eight and captured seven of the attackers, the government added.
