Lebanon on Sunday arrested a member of a pro-Syrian Islamist group, taking its first action in response to a UN report that pointed to Syrian involvement in the February assassination of Rafiq Hariri, the country's former prime minister.

As the US and Britain kept up the pressure on Syria ahead of a meeting at the UN Security Council on Tuesday, a politician close to the Syrian government said Russia and China, permanent members of the Council, had given assurances to Damascus that they would block punitive measures against Syria.