As Israeli attacks on Iran, and Tehran’s retaliatory strikes, enter their sixth day, the deepening conflict is sparking fears in Islamabad, say analysts, rooted in its complex ties with Tehran and the even greater unease at the prospect of the Israeli military’s aerial influence extending close to the Pakistani border.

Explosions were heard in Tehran early Wednesday as Israeli warplanes pounded Iran’s capital overnight and into Wednesday. Iran’s supreme leader on Wednesday rejected U.S. calls for surrender and warned that any military involvement by the Americans would cause “irreparable damage” to them.

Iran said it had conveyed to Washington that it will respond firmly to the United States if it becomes directly involved in Israel's military campaign, the Iranian ambassador to the United Nations in Geneva said on Wednesday.

Fox News' Mike Tobin has the latest on Israel's target on Iran's nuclear program on 'Special Report.'