New Delhi, March 20 - Indian Prime Minister Manmohan Singh on Wednesday said that Italy's refusal to turn over two marines to India to stand trial on murder charges "casts a shadow" over the two countries' relations. Singh also said that "the Italian position is not acceptable for India". The prime minister earlier said that all diplomatic and legal options would be explored to bring the two marines back to India to face trial. The two marines had been held in India since February 2012 after a shooting incident in international waters in which two Indian fishermen were killed. Italy has always denied that India has jurisdiction over the case, as it took place in international waters. As a sign of goodwill, the two marines were allowed to return to Italy to spend Christmas with their families and - after returning to India as agreed between the two governments - were allowed back to Italy again to vote in February elections. However, despite a written statement by Italy's ambassador to India that the pair would once again return to India, the Italian government reneged on the promise, sparking a new diplomatic tussle with New Delhi. In response, the Indian Supreme Court ordered Italy's ambassador there not to leave the country.