Karunanayake was made the new foreign minister replacing Samaraweera who got finance portfolio in addition to the new portfolio of media.
The reshuffle is being seen as a response by Sirisena on public criticism of some of his Cabinet members. This was the first reshuffle of the government since it was elected in 2015.
Karunanayake, 54, is an assistant leader of Prime Minister Ranil Wickremesinghe's United National Party (UNP).
Samaraweera, 60, had been targeted by the opposition for allegedly compromising of Sri Lanka's interests in agreeing to co-sponsor UN Human Rights Council resolutions which called for international probe on the islands human rights accountability.
Sirisena also moved the legendary cricket captain Arjuna Ranatunga from his ports and shipping portfolio to the ministry of petroleum resources.
Ranatunga's handling of the ports ministry had drawn ire from the ports trade unions. He repotedly angered both Sirisena and Wickremesinghe over his opposition to the proposed Chinese economic zone in the southern port of Hambantota.
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