Tehran has accused Washington of violating a ceasefire, vowing to respond

Iran has denounced a US attack on one of its vessels as "armed maritime piracy," warning of retaliation.

On Sunday, a US warship fired at and subsequently seized an Iranian-flagged cargo vessel in the Gulf of Oman. The military said the ship, identified as the Touska, was attempting to breach a naval blockade and head for Bandar Abbas through the Strait of Hormuz.

In a statement released shortly afterward, Iran's military command center, Khatam al-Anbiya, condemned the strike on a vessel returning from China, accusing Washington of violating the ceasefire in place since April 8.

"We warn that the armed forces of... Iran will soon respond and retaliate against this armed piracy and the US military," a spokesperson for the command center said, as cited by ISNA news agency.

US President Donald Trump announced the blockade of Iranian ports last week after Pakistani-mediated talks failed to achieve a breakthrough.

Iranian Foreign Ministry spokesman Esmail Baghaei said the US blockade of Iran's ports and coastline is an act of aggression that violates the ceasefire.

"By deliberately inflicting collective punishment on the Iranian population, it amounts to war crimes and crimes against humanity," Baghaei said on social media.

Baghaei's comments on Sunday followed renewed Iranian threats to shipping in the Strait of Hormuz in response to the US blockade, effectively reclosing the strategic route which handles around 20% of the global oil and liquefied natural gas trade.

Iran's Tasnim news agency later reported that Iranian forces launched drones toward US naval vessels. The Pentagon has not confirmed whether any ships came under attack.