UN human rights investigators said Tuesday that they have "reasonable grounds" that a limited number of chemical weapons have been used in Syria.

In its latest report, according to the victims, medical personnel and other witnesses interviewed, they say, they have received, the Syrian government forces and anti-government forces had used banned weapons charges, but most of the testimony relates to the use of state power .

"There are reasonable grounds to believe that the use of a limited number of toxic chemicals, it was not always possible to obtain evidence to determine the exact chemical agents, their delivery systems, or perpetrator," Paulo Pinheiro, who chaired the UN investigation Committee in Geneva, said at a news conference.

Commission considered four reports in March and April of toxic attacks, but can not determine which party is behind them.

"Witness, we have interviewed, including victims, refugees fleeing some areas, as well as medical staff," Pinheiro said, declining to be more specific reasons of confidentiality.

Refugees in neighboring countries, and people are still using Skype team in Syria by more than 20 investigators, from January 15 to May 15 conducted 430 interviews.