By AFP teams in Tehran, Dubai, Beijing and Mecca

An Indian police official salutes US Secretary of State Marco Rubio before he boards his plane at Jaipur International Airport in Jaipur.

US forces attacked missile sites in southern Iran and boats trying to lay mines on Monday (local time), US Central Command has said, imperilling a fragile ceasefire and casting new doubt on a deal to end the Middle East war.

The strikes came as top Iranian negotiators arrived in Doha for the latest round of talks to end the months-long conflict, and as the Israeli military stepped up hostilities with Iran-backed Hezbollah in southern Lebanon.

Oil prices fluctuated in the wake of the US strikes, which may threaten any agreement to reopen the Strait of Hormuz, where an Iranian blockade has throttled global fuel supplies.