U.N. war crimes investigators said on Monday it had become increasingly difficult to interview newly arrived Syrian refugees in European countries and urged them to improve access to help document fresh abuses.
The panel says it has compiled a confidential list of suspects on all sides that have committed war crimes or crimes against humanity. It called again for major powers to refer Syria to the International Criminal Court.
"We are appealing to countries inside Europe hosting newly arrived Syrian refugees to grant us access and remove any barriers to our work," Paulo Pinheiro, chairman of the U.N. Commission of Inquiry on Syria, told the U.N. Human Rights Council.
He did not name the European countries hampering investigators' access to Syrian refugees. Most have gone to Germany and Sweden while others remain stuck in Greece and Italy seeking asylum.
"Time is of the essence, particularly if the Commission is to continue preparing well-documented reports on the current situation in the country, rather than reports of a historical nature," Pinheiro said.
The panel said earlier this month that it had a database of some 5,000 detailed interviews and information, some of which is being shared with European governments seeking to prosecute their nationals fighting as foreign militants in Syria.
"There have been cases of successful prosecution which our information has aided," Pinheiro told the 47-member Geneva forum on Monday, without elaborating.
Carla del Ponte, a panel member and former U.N. war crimes prosecutor, said: "We need a formal investigation to be done as soon as possible. Time is passing and we must be ready for a future tribunal. Don't forget, 'no peace without justice.'"
A 20-truck aid convoy destined for the rebel-held eastern part of Aleppo with enough supplies to feed tens of thousands remains stuck in Turkey, U.N. officials said on Monday, hours after a seven-day cease-fire in Syria expired.
Julian Braithwaite, Britain's envoy to the U.N. council, cited "clear evidence" of both government and Islamic State militant forces killing civilians with chemical arms, making it crucial for U.N. investigators to hold perpetrators to account.
Moscow stepped up a war of words with Washington on Sunday, saying deadly air strikes by the U.S.-led coalition on Syrian government forces threatened the implementation of a U.S.-Russian cease-fire plan and bordered on connivance with Islamic State.
Syrian Ambassador Hussam Eddin Aala, addressing the rights council on Monday, denounced "this treacherous, deliberate, pre-planned American aggression" that he said had killed dozens of Syrian soldiers and paved the way for an Islamic State attack.
Russia has backed Syrian President Bashar al-Assad in Syria's civil war while the United States has supported non-Islamist rebel forces fighting to topple him.