The families of six sailors from India, Iraq and Pakistan have been left without answers for more than six months after two Iran-linked cargo vessels they were assigned to disappeared in Iranian waters.

The vessels, Bridge 1 and Bridge 2, were last detected near Iran's Kish Island on May 9, with no distress signals received. Their fate remains unknown, with no confirmation whether they sank or were seized by a country.

Among the missing crew members is 23-year-old Indian sailor Naveen Kumar, whose mother, V. Pandiselvi, has not heard from him since the vessels disappeared. She continues to replay his old voice messages, hoping he will return.

"We cannot bear this pain," Pandiselvi, 45, told Reuters from her home in Dindigul, in India's southern Tamil Nadu state.

"You don't need anyone to tell you what a parent would go through if they were to lose their child. We appeal to everyone involved to please come forward and help us."

Kumar was one of six crew members assigned to the two vessels, which were carrying steel and reportedly involved in Iranian trade. The other missing sailors are three Iraqis, one Pakistani and another Indian.

According to Khaled Saad al-Thaalibi, head of the Iraqi maritime foundation in Basra, the vessels' Automatic Identification System (AIS) transmitted their last known position about eight nautical miles from Kish Island at 4:50pm on May 9.

"We called the agent in Iran but he told us that he knew nothing about the incident and on the following day the Iranian search and rescue tried to look for the vessels but they found nothing," Thaalibi told Reuters.

"We don't know if the vessels sunk or were confiscated by a country."

Iraq said in May that it was monitoring the disappearance. Gulf ports had also sought information after losing communication with the crews.

The disappearance came amid growing attacks on commercial shipping since the US-Israeli war on Iran began on February 28. Tehran has attacked vessels to assert control over the Strait of Hormuz, while the United States has targeted Iran-linked ships as part of a blockade of Iranian ports.

The UN's International Maritime Organization has confirmed 130 incidents, mainly attacks, in the region since the conflict began, with at least 25 seafarers killed.

Even before the war broke out, Kumar's family had been trying to bring him home. He had left India for what he was told would be a six-month crew contract based in Dubai, but found himself in Iran just a week into the job.

His family had borrowed around 1.5 million Indian rupees ($16,000) to finance his maritime training and help him pursue a career at sea.

His mother said she had repeatedly sent him voice messages without receiving a reply. The family has kept his phone number active in the hope that he might answer.

"My mental condition had deteriorated into madness, I sent desperate messages," she said.

"A terrifying question mark hangs over his fate: Is he still on that ship, or has something terrible happened to him? It's causing a lot of confusion. Every passing minute is agony."

The family initially received assurances from Mumbai-based recruitment agency Lascar Marine that Kumar would return soon. However, agency representatives later said they had no information about his whereabouts, and subsequent calls went unanswered.

An order published on a government website showed that India's Seamen's Employment Office withdrew Lascar Marine Services' recruitment licence on May 22 and barred its former and current directors from maritime business for five years. The action cited repeated failures to repatriate seafarers, including Kumar, or pay their wages.

The disappearance has also devastated the family of Iraqi sailor Haider Rahman al-Mayahi, 22, whose brother Youssef Rahman said he left behind a one-year-old daughter and a father who suffered a stroke following the news of his disappearance.

Al-Mayahi's family travelled to Iran in search of answers and located the vessels' owner, whom they identified as an Iranian national. He told them he had no information about the ships.

The families have received conflicting accounts of what might have happened. Some shipping sources believe the vessels may have been struck by US forces and sunk, while others speculate that the crews could have been detained by Iran or a Gulf state.

The Iranian agent who recruited the Iraqi sailors did not respond to Reuters' calls. Lascar Marine and India's Seamen's Employment Office director also did not respond to requests for comment.

The risks of working in the region have also driven up seafarers' wages. Shipping sources said the cost of hiring crew members had tripled since the war began, with some sailors now earning in a single voyage what they previously made in seven months.

For Kumar's mother, however, the prospect of higher earnings has lost its meaning.

"We worked tirelessly to secure our children's careers and future," she said. "Now, seeing everything that has happened, we are left wondering what our lives have come to."