New Delhi, April 19 -- Iran's Revolutionary Guard fired at two Indian-flagged merchant vessels in the Strait of Hormuz on Saturday, prompting the external affairs ministry to call in the Iranian envoy to lodge a formal protest over the incident. This was the first instance of Iran's Islamic Revolutionary Guard Corps (IRGC) firing at Indian-flagged or owned merchant shipping in the crucial waterway, which is used to transport 50% of India's oil imports. In recent weeks, at least nine Indian-flagged vessels have safely transited the strait. The shipping ministry in a status update said that an oil tanker, the MT Desh Garima, transited the strait at 1pm IST and is bound for Mumbai. Thirteen India-flagged ships remain in the Persian Gulf, west of the Strait of Hormuz. It also said that two India-flagged vessels were reportedly fired at by the IRGC boats during transit, identifying the vessels as the Sanmar Herald, a crude oil tanker and the Jag Arnav, a bulk carrier. The two turned back after the incident and no injuries were reported, the ministry said. Iranian ambassador Mohammed Fathali was "called in" by the external affairs ministry for a meeting with foreign secretary Vikram Misri on Saturday evening, ministry spokesperson Randhir Jaiswal said. "During the meeting, the foreign secretary conveyed India's deep concern at the shooting incident earlier today involving two Indian-flagged ships in the Strait of Hormuz," Jaiswal said. Misri noted the importance that India attached to the safety of merchant shipping and mariners and recalled that Iran had earlier facilitated the safe passage of several ships bound for India, Jaiswal said. "Reiterating his concern at this serious incident of firing on merchant ships, foreign secretary urged the ambassador to convey India's views to the authorities in Iran and resume at the earliest the process of facilitating India-bound ships across the strait," Jaiswal said. Significantly, the external affairs ministry used the term "called in" - which in diplomatic parlance is considered less harsh than the summoning of an envoy to lodge a formal protest. Fathali undertook to convey the Indian side's views to Iranian authorities, Jaiswal said. The incidents of firing on the Indian-flagged vessels occurred after Iran's supreme national security council said it would resume control over the Strait of Hormuz "until the end of the war is definitively concluded". The body warned that as long as the US blockade of Iranian ports continues, Iran will "regard it as a breach of the ceasefire and will prevent the conditional and limited reopening of the strait of Hormuz". The external affairs ministry did not provide details of the Indian-flagged vessels that were targeted. The UK's Maritime Operations Centre, which tracks attacks on merchant shipping in the region, said it received a report of an incident 20 nautical miles northeast of Oman, with the master of an oil tanker reporting that the vessel was approached by two IRGC gun boats without any challenge on radio. The gun boats "then fired upon the tanker", the Centre said. The tanker and its crew were reported safe, it said. People familiar with the matter said the tanker was the Sanmar Herald. The UK Maritime Operations Centre said it received another report of an incident 25 nautical miles northeast of Oman, in which a container ship was "hit by an unknown projectile which caused damage to some of the containers". There were no fires or environmental impact reported, the Centre said. The people cited above said this too was an Indian-flagged vessel. The Indian government, in its interactions with the leadership of Iran, the US and key West Asian states, has emphasised the need to ensure the safe and unimpeded passage of merchant vessels through the Strait of Hormuz. It has also emphasised the importance of dialogue and diplomacy in ending the West Asia conflict....