The authorities of the northern Somali region of Somaliland on Friday seized a plane carrying military supplies to Puntland, a neighbouring and rival self-proclaimed state, officials said.

Somaliland's interior minister, Mohamed Abdi Gabose, told reporters in the regional capital Hargeysa that the cargo plane was in violation of the international arms embargo on Somalia.

"The aircraft was originally coming from South Africa and Kampala. They asked for permission to land at our airport after experiencing a fuel shortage," Gabose said.

"But it landed before we officially gave our green light and we have seized the plane," he said, adding that the six crew members were arrested.

"This aircraft was heading to Puntland and carried military uniforms as well as other supplies for the newly recruited militiamen," the minister said.

Puntland, on whose shoreline are most of the main bases for the pirates marauding on the Gulf of Aden and Indian Ocean, has enlisted private security company Saracen International to train a dedicated anti-piracy force.

The move sparked criticism from the Pentagon, which said it was concerned at the lack of transparency regarding the programme's funding.

Tensions also run high between Somaliland and Puntland, which are separated by a disputed territory where armed clashes sporadically break out.

"This company that is training the militiamen is doing illegal business and violated the international arms embargo on Somalia," Gabose said.

"The military training provided to Puntland is a threat to Somaliland's security and to that of the region in general," he said.

Airport officials said heavy security was deployed around the plane, as its cargo and manifest were being further investigated.