Cyprus has condemned a Turkish naval exercise off the divided island's coast as "illegal", ahead of a visit by top US diplomat Mike Pompeo to discuss heightened tensions in the Mediterranean.

Ankara is at loggerheads with Greece and Cyprus over maritime hydrocarbon resources and naval spheres of influence, sparking fears of conflict.

In a message on NAVTEX, the international maritime navigational telex system, Turkey gave notice on Friday of a gunnery exercise off the coast of Sadrazamkoy in northern Cyprus. In response, Cyprus' Joint Rescue Coordination Centre -– attached to the defence ministry -- late Friday called Turkey's move "illegal" because it "violates the Republic of Cyprus' sovereignty and sovereign rights."

The Mediterranean island is divided between the internationally recognised Republic of Cyprus, a member of the EU, and a breakaway state set up after a Turkish invasion launched in 1974 in response to a coup sponsored by the military junta then ruling Greece.

Ankara's military exercise off Cyprus, taking place between Saturday and Monday, comes despite the looming threat of EU sanctions. In a separate development, the Greek Cypriot National Guard said Saturday that it would take part in joint training manoeuvres with US forces and two boats.

"Two combatant craft medium transport vessels of the US special navy forces are in Cyprus to participate in joint military drills," it said in a statement.

The drills, which began Saturday and will last until September 20, are taking place in the "framework of the bilateral relations between the Republic of Cyprus and the US."

Pompeo is expected in Cyprus early on Saturday evening, and is due to hold talks with the EU member state's President Nicos Anastasiades. Pompeo has said his trip to Cyprus would complement phone calls by President Donald Trump with his Turkish counterpart Recep Tayyip Erdogan and Greek Prime Minister Kyriakos Mitsotakis.

On Thursday, southern European leaders warned they were ready to back EU sanctions against Turkey if Ankara shunned dialogue. The issue will be discussed again at an EU summit on 24-25 September.

Tensions escalated after Turkey sent the Oruc Reis seismic research vessel and a small navy flotilla to waters claimed by Greece on August 10.

Greece then responded by shadowing the Turkish ships and staging naval exercises with several EU allies and the United Arab Emirates in its own show of force.

The Oruc Reis is supposed to remain in the disputed waters until Saturday.