The Turkish and Russian presidents, who back opposing sides in the Libyan conflict, have called for a ceasefire in the war-torn country to begin at midnight on Sunday, January 12.

Recep Tayyip Erdogan was joined by Vladimir Putin in Istanbul on Wednesday to inaugurate a new pipeline carrying gas to Europe, but the pair commented on the Libyan situation and rising US-Iran tensions.

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In a joint statement, Turkey and Russia called on all parties in Libya to "declare a sustainable ceasefire, supported by the necessary measures to be taken for stabilising the situation on the ground and normalising daily life in Tripoli and other cities".

They also said Washington and Tehran should prioritise diplomacy, warning that the recent exchange of attacks could lead to a new cycle of instability in the region.

In Libya, Turkey backs Fayez al-Sarraj's Tripoli-based Government of National Accord (GNA), which is recognised by the United Nations, while Russia has sent support to renegade military commander Khalifa Haftar's opposing forces to the east.

Ankara has said it will send troops to Libya upon the GNA's request.

Early on Wednesday, Iran fired missiles at military bases housing US troops in Iraq in retaliation for the US assassination of Qassem Soleimani, Iran's leading military commander, raising the stakes in Tehran's conflict with Washington amid concern of a wider conflict in the Middle East.

Putin and Erdogan were speaking at the launch of the TurkStream pipeline, which will carry Russian natural gas to southern Europe through Turkey - part of Moscow's efforts to reduce shipments via Ukraine.

The pipeline project, stretching 930 kilometres (580 miles) across the Black Sea, reinforces strong energy ties between Moscow and Ankara, which were boosted after Turkey bought advanced S-400 Russian missile defence system last year.

Russia and Turkey also coordinate in northeast Syria, although they back opposing sides in the conflict in the northwest Idlib region.