At least 101 sailors are missing and 78 wounded after a submarine attack on an Iranian ship off Sri Lanka's coast.
If sunk, that would be the first time a submersible has destroyed a navy vessel in war in decades.
There was no immediate comment from the US, which has its fleet in the Arabian Sea and Indian Ocean. Reuters reported the sinking and casualty figures, quoting naval sources.
Sri Lanka's military has rescued at least 30 people. Foreign Minister Vijitha Herath told parliament that injured sailors were taken to hospital in the island's south.
Sri Lankan media said the ship made a distress call off the coast of Galle in the southern part of the country and that the injured had been admitted to hospital there for treatment.
In parliament, a member of the opposition asked whether the vessel had been bombed as part of the US-Israeli attacks on Iran, but there was no immediate response from the government.
Navy spokesman Buddhika Sampath said the rescue operation was in line with Sri Lanka's maritime obligations.
The conflict between the US, Israel and Iran has escalated into a regional war after coordinated strikes were launched on Iran on Saturday.
The joint operation, code-named Operation Epic Fury by the US and Operation Roaring Lion by Israel, has entered its fifth day, with hundreds of Iranian military sites being attacked and the regime's leadership targeted.
