Three seafarers have died and seven more taken to hospital after being exposed to toxic fumes on a cargoship off Azerbaijan.

The Iranian-flagged 2,800-dwt Nezmehr (built 1998) was heading from Kazakhstan to Baku when the incident occurred 21 miles offshore in the Caspian Sea.

Toxic fumes from a grain cargo have been blamed.

The families of those who died will receive compensation, Iran's ambassador to Azerbaijan Javad Jahangirzadeh told the Trend news agency on Friday.

"The crew of the cargoship got poisoned on the Kazakh border. They tried to quickly reach the Azerbaijani coast. Fortunately, the forces of the coast guard of Azerbaijan came to the rescue and the victims were hospitalised," Jahangirzadeh said.

The three who died were Iranian citizens. The condition of their colleagues was said to be stable.

The ownership of the vessel is not known.