Libya's eastern-based government linked to military commander Khalifa Haftar opened an embassy in Syria on Tuesday and called for the two countries to unite in their common fight against Turkey-backed militant groups.
Syria has faced resistance from Turkish forces allied to rebels in its northeast.
Libya has two governments, one based in the capital Tripoli and widely recognized internationally, and another based in the east. Eastern commander Haftar has launched an assault to capture Tripoli, and is fighting forces aligned with the government there which are backed militarily by Turkey.
"Terrorism will kill any Arab country if it's permitted and if the criminal (President Tayyip) Erdogan is permitted to win this fight," Syria's deputy foreign minister Faisal Mekdad said at a ceremony to open the embassy.
President Bashar al-Assad has looked to shed his country's pariah status and regain Arab support. The United Arab Emirates, which backs Haftar in Libya, re-opened its Damascus embassy in December 2018 and has forged closer ties after once supporting rebels fighting against Assad.
Libya's diplomatic missions are generally aligned with the government based in Tripoli, but diplomats in some foreign capitals have supported the rival government based in the east.