RTS has reported that the Swiss government trained Syrian rebels in Geneva Conventions' protocol in November.
The training in the rules of war took place near Lake Geneva in mid-November, with 15 Syrian participants.
It was kept secret until now for security reasons.
Who participated in the training is unclear but reports claim it included rebels both within and outside Syria.
A spokesperson for the Swiss Foreign Affairs Department told RTS: "80 percent of the violations and war crimes are likely committed by the regime but the opposition commits them as well, notably with the summary execution of prisoners. Switzerland condemns violations on both sides."
Syrian rebels have been accused of violating human rights and violating the rules of war on numerous occasions during the nearly two-year revolt.
On Monday, Human Rights Watch issued a report about rebel attacks on places of worship, which are against the Geneva Conventions.
The rights group wrote:
While some opposition leaders have pledged to protect all Syrians, in practice the opposition has failed to properly address the unjustified attacks against minority places of worship.
Switzerland's neutrality means that it must walk a fine line in its involvement in foreign wars.
Many cite its booming weapons industry as a violation of that neutrality.
Geneva Lunch said the Department of Foreign Affairs in Switzerland will continue to encourage training of Syrian rebels in the rules of war.