CAIRO/TEHERAN/ISTANBUL/MOSCOW - Iran has deployed one of its largest missiles at an underground facility unveiled Wednesday, Iran's Fars News Agency reported Thursday.

Fars said the Khorramshahr-4 long-range ballistic missile was among the operational assets displayed during the opening of the site, which is operated by the Aerospace Force of the Islamic Revolutionary Guard Corps (IRGC).

The agency, close to the IRGC, described the Khorramshahr-4 as one of the country's advanced medium- to long-range ballistic missiles, with an estimated range of about 2,000 kilometers.

The warhead is capable of carrying more than one ton of high-explosive payload, the report said, making it "one of the largest warhead configurations developed within Iran".

During last June's 12-day conflict, Iran fired the Khorramshahr-4 at Israel in retaliation for US strikes on Iranian nuclear-related targets.

Iran and the United States are scheduled to hold talks on Friday in Muscat, Oman, amid a recent US military buildup in the Middle East and Teheran's stepped-up preparations.

'Secure national interests through diplomacy'

On Thursday, Iran's Foreign Ministry spokesperson Esmaeil Baghaei stressed that Iran will not miss any opportunity to secure its national interests and maintain regional peace through diplomacy.

Noting that an Iranian delegation headed by Foreign Minister Seyyed Abbas Araghchi has departed for Muscat, Baghaei wrote that the discussions aim to reach "a fair, mutually agreeable and honorable understanding (between the two sides) on the nuclear issue".

Iran hopes that Washington "will also participate in this process with responsibility, realism and seriousness", he wrote on the social media platform X.

Two vessels carrying smuggled diesel seized

Separately, the IRGC said its naval forces have seized two vessels carrying smuggled fuel near the Farsi Island in the Persian Gulf.

In a statement on its official news outlet Sepah News, the IRGC said that after seizing the vessels with a judicial order and transferring them to the southern port city of Bushehr, its forces detained 15 foreign crew members on board the ships and handed them over to the country's judicial authorities for legal proceedings.

It added that the two vessels were carrying more than 1 million liters of smuggled diesel, noting that they were part of a network involved in smuggling fuel over the past months and were identified and confiscated on the back of the monitoring and tracking by the IRGC Navy's intelligence forces.

Iran-US situation 'highly explosive'

Meanwhile, Russian Foreign Minister Sergei Lavrov said the situation between Iran and the United States is highly explosive.

"Right now, we are not imposing ourselves as mediators between Iran, Israel and the United States. In our contacts with them, we are simply discussing the developments," Lavrov said in an interview with Russia Today, noting that as Iran's close partner, Russia is closely monitoring the unfolding situation.

He said that Russia stands ready to contribute to the de-escalation of tensions and ensure compliance with existing agreements.

"There are far too many ticking time bombs waiting to be set off by a clumsy misstep. The Iranians and Israelis know that we are prepared to facilitate the implementation of any agreements that may be reached," Lavrov added.

Negotiation process 'still alive'

Speaking to journalists aboard his flight back from visits to Saudi Arabia and Egypt, Turkish President Recep Tayyip Erdogan stressed the negotiation process between the United States and Iran is "alive and not broken" and the "ground remains open to dialogue and diplomacy" to ease tensions.

Erdogan said he sees both sides willing to leave room for diplomacy, calling it a positive development.

The way to resolve problems is not through conflict, but through reconciliation and negotiation, he noted, adding that Turkiye will work to strengthen the basis for negotiations through both leader-to-leader diplomacy and talks at other levels.

Ali Shamkhani named secretary of Defense Council

In another development, Ali Shamkhani, senior advisor to Iranian Supreme Leader Ali Khamenei, has been appointed as secretary of the country's newly-formed Defense Council, Fars reported Thursday.

The appointment was made in a decree issued by Iranian President Masoud Pezeshkian, according to Fars.

Shamkhani had previously been appointed by Khamenei as his representative in the council. He served as Secretary of Iran's Supreme National Security Council from 2013 to 2023.

Also an incumbent member of Iran's Expediency Discernment Council, Shamkhani was severely injured in an Israeli airstrike targeting his house in Teheran in June last year during the 12-day conflict between Iran and Israel.

READ MORE: Iran approves formation of new defense council

Presided over by Iran's president, the Defense Council was established in August 2025 following the conflict to review the country's defense plans and the improvement of the Iranian armed forces' capabilities in a centralized manner.