Sri Lanka’s military campaign against the Tamil Tiger rebels is no longer a purely domestic affair. The UN Security Council got involved early on Thursday, saying it was “gravely concerned” at the plight of tens of thousands of civilians caught up in what may be the Tigers’ final battle. The UN says they are being used as human shields.After 25 years of conflict and from controlling nearly a third of the country, the Tigers are left holding a tiny strip of the north-eastern coast. The government says it has stopped using artillery in such a densely-populated area, but reports talk of daily use of heavy weapons. The UN move puts pressure on the government to end the situation quickly.