SINGAPORE (AFP) - Two oil tankers have been stopped from leaving a rebel-held port in war-torn Yemen over a commercial dispute, the ships' Singapore-based owner said on Friday (Sept 15).

The Singapore-flagged Chao Hu and Hong Ze Hu - both carrying crude oil - have been prevented from leaving Hodeida, the second-largest port in Yemen, an impoverished country that is heavily dependent on imports.

"The vessels themselves are not under arrest but have unfortunately been caught up in a commercial dispute between cargo interests," the ships' owner, Ocean Tankers, told AFP in a statement.

"The dispute is nothing to do with Ocean Tankers or our ships and we hope the dispute can be settled quickly," the company said, providing no further details.

According to ship tracking data seen by AFP, both the Chao Hu and Hong Ze Hu have been anchored in the Red Sea for at least four months.

Shipping has become increasingly dangerous around Yemen, the poorest country in the Arab world, since fighting erupted two years ago.

The Iran-backed Huthi rebels overran the capital Sanaa unopposed in September 2014 and went on to expand their control of the impoverished country, advancing to southern provinces, including the Hodeida port.

The violence has intensified since the collapse in early August of UN-mediated peace talks held in Kuwait, with military sources telling AFP that 40 people were killed in fighting between rebels and pro-government forces on Wednesday.

Meanwhile importers are struggling to pay for essential goods as the country's foreign currency reserves shrink, with aid agencies warning that millions are on the brink of famine.

Yemen's conflict has killed more than 6,600 people, most of them civilians, and displaced at least three million others, according to the United Nations.