(Reuters) -- Libya will do all it can to protect its 75 percent stake in Zamtel, the fixed-line telecoms firm in Zambia, whose government announced plans last week to seize Libya's stake in the firm, Libyan Foreign Minister Ashour bin Khayyal said Monday.

The Zambian government has taken a unilateral action by nationalizing this company, Khayyal said, adding he had spoken to his Zambian counterpart about the issue at the African Union summit in Addis Ababa, Ethiopia.

Zambia dissolved the board of Zamtel and appointed a new acting CEO last Tuesday, a day after announcing plans to seize 75 percent of the firm from Libya's LAP Green Networks.

The previous Zambian government had sold the 75 percent stake to LAP Green Networks for $257 million in 2010.

Libya made major investments in Africa during Muammar Gaddafi's rule, some of them managed by the $65 billion Libyan Investment Authority (LIA) through a $5 billion fund known as Libyan African Investment Portfolio.

LAP, a telecom company operating in six African countries, was one of these investments.

Khayyal said Libya's ruling National Transitional Council would review such investments. We will keep what (investment) is successful, and we will review what is facing difficulty or is a failure, he told Reuters on the sidelines of the summit.

He said Libya would send a delegation to Zambia to discuss the Zamtel issue in one or two weeks.

Definitely this money is Libyan money, and owned by the Libyan people. We will exercise all our efforts to protect this money, Khayyal said.

(Reporting by Yara Bayoumy; editing by Tim Pearce)