WASHINGTON/DUBAI/Islamabad, April 23 -- Iran seized two ships in the Strait of Hormuz on Wednesday, tightening its grip on the strategic waterway after US President Donald Trump called off attacks indefinitely with no sign of peace talks restarting. Iran's semi-official Tasnim news agency said that the Revolutionary Guards had seized two vessels for maritime violations and escorted them to Iranian shores. It was the first time Iran has seized ships since the war began at the end of February. The Revolutionary Guards also warned that any disruption to order and safety in the strait would be considered a "red line", Tasnim said. Earlier, a British maritime security agency reported that three ships had come under fire. Trump said in a statement on social media late on Tuesday that the US had agreed to a request by Pakistani mediators "to hold our Attack on the Country of Iran until such time as their leaders and representatives can come up with a unified proposal ... and discussions are concluded, one way or the other." But even as he announced what appeared to be a unilateral ceasefire extension, Trump also said he would continue the US Navy's blockade of Iran's trade by sea. The US fired on and seized an Iranian cargo vessel on Saturday and boarded a huge Iranian oil tanker on Tuesday in the Indian Ocean. Iran considers the US blockade an act of war and has said that as long as it continues it will not lift its closure of the strait, which has caused a global energy crisis. In a show of defiance, Iran showcased some of its ballistic weapons at a parade in Tehran on Tuesday evening, with images on state TV showing large crowds waving Iranian flags and a banner in the background with a fist choking off the strai Pakistan, which has acted as a mediator, was still trying to bring the sides together for negotiations after both failed to show up for last-ditch talks on Tuesday before the two-week-old ceasefire had been due to expire. "We were all prepared for the talks, the stage was set," a Pakistani official briefed on the preparations told Reuters. "If you ask me honestly, it was a setback we were not expecting, because the Iranians never refused, they were up to come and join, and they still are." Another Pakistani source who was involved in the talks said Pakistan was still "working very hard to bridge that conflict, talk to each side with their sensitivities in mind". There was no response early on Wednesday to Trump's ceasefire announcement from senior Iranian officials, although some initial reactions from Tehran suggested Trump's comments were being treated skeptically. Tasnim said that Iran had not asked for a ceasefire extension and repeated Tehran's threats to break the US blockade by force. Throughout the war, Iran has effectively shut the strait to ships other than its own by attacking vessels that attempt to transit without its permission. Around a fifth of global oil and liquefied natural gas normally passes through the waterway. On Wednesday, Britain's maritime security agency UKMTO said that at least three container ships had reported being hit by gunfire in the strait. The master of one ship reported being approached by an Iranian gunboat northeast of Oman on Wednesday, the agency said. The vessel came under fire from guns and grenades and its bridge was heavily damaged, although there were no reports of casualties or environmental damage. Two other ships had said they came under fire about eight nautical miles west of Iran with no reported injuries. Iran has condemned the US Navy intercepting Iranian ships as part of its blockade, accusing it of "piracy at sea and state terrorism". With his announcement on Tuesday, Trump again pulled back at the last moment from warnings to bomb Iran's power plants and bridges, a threat condemned by the United Nations and others as potentially constituting war crimes. Iran had said it would strike its Arab neighbours if its civilian infrastructure was hit....