Washington (CNN) Secretary of State John Kerry on Friday accused Russia of bombing women and children "in large numbers" in Syria.

Speaking to reporters in Washington, he said the Russian bombing campaign was not precise and that the Russians were using "dumb bombs."

"This has to stop," Kerry declared.

Kerry also continued to push for a ceasefire in Syria.

"The Russians have made some constructive ideas about how a ceasefire could in fact be implemented, but if it's just talk for the sake of talk in order to continue the bombing, nobody's going to accept that. And we will know that in the course of the next days."