More than 200,000 people have fled Aleppo in recent weeks, the UN says, as government forces battle to oust Free Syria Army (FSA) rebels from the country's biggest city.
She urged both sides to show restraint and to distinguish between civilians and fighters in the conflict.
Meanwhile, reports suggest army troops have killed 35 people near Damascus, most of them unarmed civilians.
They died after government forces shelled and overran the neighbourhood of Jdeidet Artouz, southwest of the capital, on Wednesday, activists and residents told Reuters.
On Wednesday, video footage emerged apparently showing the public shooting of four Assad loyalists by rebels in Aleppo, sparking criticism from human rights groups.
The rebels appear to control large parts of the city despite government assertions that they have suffered heavy losses.
The UK-based Syrian Observatory for Human Rights reported 135 deaths on Wednesday while the Local Coordination Committees gave a figure of 170.
"In the last 72 hours we saw a significant increase in the level of violence. Our observers are reporting heavy exchanges of fire," Ms Ghosheh said on Wednesday.
"They also reported the use of helicopters, tanks, heavy machine guns and artillery. Yesterday, for the first time we saw firing from fighter aircraft."