The first contingent of United Nations military observers took up positions along the Strait of Hormuz on Thursday morning, hours after mediators in Islamabad and Doha began an intense round of phone diplomacy to contain the earliest violations of an Iran-Israel ceasefire that had held for barely 36 hours.

A 14-member advance team, drawn from the existing UN Truce Supervision Organization and bolstered by liaison officers from Norway, Finland and Indonesia, established a temporary command post on Oman’s Musandam peninsula and began monitoring shipping lanes from a leased coast-guard cutter, according to a statement from the UN Department of Peace Operations. A larger 60-person mission is expected to be in place by April 22 under a Security Council resolution adopted Monday.

The deployment came against the backdrop of two incidents that tested the framework brokered in Islamabad. Just before dawn local time, Houthi forces in Yemen fired a single medium-range ballistic missile in the direction of southern Israel; the missile was destroyed by an Arrow interceptor over the Red Sea, according to the Israel Defense Forces. Several hours later, a Katyusha-style rocket fired from a desert tract north of Mosul fell on the perimeter of a coalition logistics annex near Erbil airport, wounding a contractor and damaging a vehicle but causing no fatalities, U.S. Central Command said.

Both attacks were condemned within hours by every signatory to the ceasefire framework, including Tehran. Iranian Foreign Minister Abbas Araghchi, addressing reporters in Tehran on the margins of a cabinet session, said Iran “neither authorized nor welcomed” the launches and would coordinate “in writing and through trusted channels” with mediators to ensure no further violations from groups it influenced. He stopped short, however, of explicitly naming the Houthis or the Iraqi militia faction most analysts blamed for the Mosul-area rocket.

“This is the test we said would come, and it has come on day two,” said Vali Nasr, a Middle East scholar reached by telephone in Washington. “What matters now is not whether shots are fired but whether the people who fire them are isolated quickly by the very governments that used to underwrite them. That is the new bargain Tehran agreed to in Islamabad, and we are watching it play out in real time.”

The Pakistani Foreign Ministry, which has continued to host a slimmed-down secretariat of mediators in Islamabad since Saturday’s announcement, issued a brief statement Thursday afternoon confirming that Foreign Minister Ishaq Dar had spoken in the previous 24 hours with counterparts in Tehran, Riyadh, Cairo, Muscat, Doha and Washington, as well as with Israeli National Security Adviser Tzachi Hanegbi. “All parties have reaffirmed their commitment to the ceasefire and to the verification annex,” the statement said, while urging “non-state actors in all theaters” to “cease activity that could threaten the framework.”

In Doha, where Qatar is expected to host the prisoner-exchange phase scheduled for April 18, the foreign ministry confirmed Thursday that technical teams from Iran, the United States and the International Committee of the Red Cross had completed a second day of meetings on the logistics of the swap. Under terms outlined in the Islamabad statement, Iran is expected to release approximately 40 detained foreign nationals, including a handful of dual-national academics and journalists held since before the war, alongside the remains of an as-yet-unspecified number of U.S. service members killed during the conflict. The United States and Israel are expected to release Iranian and Hezbollah-affiliated prisoners, including several Iranian Revolutionary Guard officers detained in third countries. A senior Qatari official, speaking on condition of anonymity in line with ministry practice, said the lists had been “substantially reconciled” but that final figures would not be released until the exchange itself.

European foreign ministers, who held a hastily convened meeting in Paris on Wednesday afternoon, used a follow-up call Thursday to agree that the EU would contribute eight observers and a maritime patrol aircraft to the Hormuz mission. EU High Representative Kaja Kallas, briefing reporters in Brussels, said member states had also begun “scenario work” on a possible easing of certain humanitarian-sector sanctions during the verification window, while stressing that “the broader sanctions architecture remains entirely intact and is not part of the truce.”

Beijing and Moscow, which had pushed harder language on sanctions relief during the UN debate earlier in the week, sounded more restrained on Thursday. Chinese foreign ministry spokesperson Mao Ning told the daily briefing in Beijing that China “supports the deployment of monitors” and called on “all sides to exercise self-restraint.” Russian Foreign Minister Sergei Lavrov, in a separate appearance, said Moscow expected to send two officers to the UN mission and would also offer technical support to a parallel Iranian-Russian working group on civilian shipping insurance.

For all the diplomatic activity, the immediate test of the framework remained out of the diplomats’ direct control. The Houthi political bureau in Sanaa, in a statement issued Thursday evening, said it remained “in full solidarity with the Iranian people” but had “received the message from our brothers in Tehran” and would observe a “voluntary pause” pending consultations. The wording stopped well short of an outright commitment to the ceasefire and left open whether further launches would resume if Yemen’s economic isolation continued.

In Iraq, Prime Minister Mohammed Shia al-Sudani convened an emergency meeting of his national security council and announced the arrest of three men in a village west of Mosul, describing them as a “fringe cell” not affiliated with any of the established Popular Mobilization Forces brigades. U.S. officials, briefing reporters in Baghdad, accepted the framing but said they would press for “more durable” guarantees against further rocket fire in coming days.

“Day one was easy because everyone was watching. Day two and day three are when the muscle memory of a six-week war starts to assert itself,” said Layla Hassan, a Beirut-based regional analyst at the Levant Policy Institute. “The mediators understand that. The question is whether they can keep moving faster than the spoilers.”

Officials in Islamabad said the secretariat would remain in place at least through the prisoner exchange on Saturday, and that a more detailed schedule for the next phase of verification talks, including the disputed nuclear-file annex, would be released after the swap is complete.