Foreign ministers from the Group of Seven industrialised nations have rejected Boris Johnson's call for targeted sanctions against senior Russian and Syrian figures.

The foreign secretary had hoped to persuade G7 ministers at a meeting in Lucca in Italy, but the group said there must be an investigation into last week's chemical weapons incident in a rebel-held town before new measures could be adopted, according to a UK government source.

The option of sanctions will remain on the table, the source said.

Italian foreign minister Angelino Alfano, who called the summit "a political success", said: "There was a prevalent position, which is very similar to the Italian one. We must have a dialogue with Russia and we must not push Russia into a corner."

The outcome of the G7 meeting will be a disappointment for the government, which had hoped to strengthen the hand of US Secretary of State Rex Tillerson as he heads to Moscow

Mr Tillerson will attempt to persuade Russian President Vladimir Putin to abandon his Syrian ally, President Bashar al-Assad, who is blamed for the chemical attack, at a later meeting.

Mr Johnson's plan for targeted sanctions against military figures was intended to overcome German and Italian objections to the adoption of wider measures against Russia and Syria.