TEHRAN -?Iran's Foreign Ministry spokesperson Esmaeil Baghaei said Tehran is in constant contact with Beirut to ensure the ceasefire commitments in Lebanon are implemented, semi-official Fars news agency reported Saturday.

Speaking from Pakistan's Islamabad, where US-Iran formal negotiations to end the hostilities in the Middle East have kicked off with the participation of the Pakistani side, Baghaei said the Iranian delegation has held talks with Pakistan, and has conveyed clearly its positions and demands, Fars reported.

Baghaei added that ceasefire violations were observed on Saturday, Fars reported.

On Feb 28, Israel and the United States launched joint attacks on Tehran and several other Iranian cities, killing Iran's then Supreme Leader Ali Khamenei, along with senior military commanders and civilians. Iran responded by launching waves of missile and drone strikes targeting Israel and US interests in the Middle East, and tightened control over the Strait of Hormuz.

A two-week ceasefire reached between Iran and the United States took effect on Wednesday. Yet Israel has said the ceasefire does not cover the conflict in Lebanon, and carried out its largest single-day attack on Lebanon on Wednesday, killing more than 300 and injured over 1,100.

On Friday, Iranian Parliament Speaker Mohammad Baqer Qalibaf, who heads the Iranian delegation in the Islamabad talks, demanded a ceasefire in Lebanon and the release of Iran's blocked assets prior to the commencement of negotiations with the United States.

Earlier on Saturday, Israeli warplanes intensified their air campaign on southern Lebanon, killing at least 13 people, including emergency and health workers.

Meanwhile, Iran's semi-official Tasnim news agency reported that Washington had agreed to unfreeze the Iranian assets, and that the Iranian delegation in Pakistan was seeking to make sure about the issue. However, several media reports, citing an unnamed US senior official, denied the report.

Tasnim reported later that as Israel has agreed to limit its strikes on southern Lebanon and that Washington intends to release Iran's blocked assets, the Iranian delegation decided to negotiate those two issues in Islamabad to resolve them completely.

Also on Saturday, several US navy ships have reportedly crossed the Strait of Hormuz.