International, Bureau Desk| Diplomatic tensions have escalated between India and the US following attacks on three separate merchant ships in a span of four days off the coast of Oman. India summoned the American diplomat twice and lodged a strong protest. The State Department said the use of lethal force against civilian shipping is unacceptable and undermines the security and stability of international maritime commerce in a sensitive area. India urged the US to ensure that US forces deployed in the region take all necessary measures to prevent further loss of civilian lives.