KABUL (Reuters) - The death toll from an attack on Kabul University has risen to at least 35, two government sources said on Tuesday, as students protested over the attack and the country marked a day of mourning.Gunmen barged into the university on Monday, in what was the second attack on an educational institution in the capital in just over a week. Both have been claimed by Islamic State. The two sources told Reuters that most of those killed were students and around 50 more people were wounded, some of them breaking limbs while jumping from windows to flee from the attack during morning classes. Officially the death toll stands at 22 with 27 wounded, according to the interior ministry. The country held a day of mourning on Tuesday, with many flags flying at half mast.