Libya's investment authority says it is suing Zambia's government for seizing its controlling share in a mobile phone network.

A Libyan telecommunications enterprise that owns 75 percent of the Zamtel network says the seizure last year by the government of newly elected President Michael Sata was "illegal and unconstitutional."

The investment authority said in a statement that the network filed demands Monday at the Zambia High Court for $480-million worth of compensation in asset value along with unspecified additional payouts for operating losses should the business not be handed back.

It said the Libyan network took over a bankrupt local company two years ago and increased its subscribers by 600 percent and revenues by 50 percent. It said other international legal steps can also be taken.