Washington (AFP) - The United States is to review staffing on a hotline to report ceasefire violations in Syria after some volunteers had trouble understanding Arabic speakers.

State Department personnel in Washington are manning a line to allow witnesses in Syria to report breaches in a tentative truce between rebels and regime forces.

But in recent days reports have surfaced that callers from the Middle East have found it hard to explain the details of alleged air and artillery strikes.

According to non-profit news organization "Syria Direct" one US official mistook "Harbnifsah" -- a frontline village -- for "Harb Bebsi" or "Pepsi War."

The report said some reporters and activists have given up on the US line and are instead reporting breaches to the United Nations or to the opposition.

On Wednesday, spokesman Mark Toner admitted that US staff -- volunteers from other departments "some of whom speak Arabic" -- had had some difficulties.

"These are State Department employees who are doing this in addition to their usual jobs," he said.

"We are aware that there were some language issues, and we're working to correct those, because it's important that we have Arabic speakers that are able to field incoming calls."

A ceasefire was declared in Syria's almost five-year civil war on Saturday, but there have already been many reports of violations.

The United States, Russia and countries in the International Syria Support Group have set up a network of monitoring centers to probe the reports.

The White House said Wednesday it was "concerned" about claims that Bashar al-Assad's regime is again bombarding civilians with tank and artillery fire.