The Lachin corridor, the only land route giving Armenia direct access to Nagorno-Karabakh, has been blocked since Dec. 12, when protesters claiming to be environmental activists stopped traffic by setting up tents.
Armenia last month told judges at the World Court, formally known as the International Court of Justice, that neighbouring Azerbaijan's blockade was designed to allow "ethnic cleansing", a claim rejected by Baku.
Armenia's foreign ministry welcomed the court's decision and called on the international community to ensure Azerbaijan immediately implemented the ruling.
"Armenia will closely monitor the situation and inform the court of any violations by Azerbaijan," it said in a statement.
Nagorno-Karabakh is internationally recognised as part of Azerbaijan, but its 120,000 inhabitants are predominantly ethnic Armenians and it broke away from Baku in the first of several wars in the early 1990s.
The court said on Wednesday it had evidence that traffic through the corridor was still disrupted, causing "shortages of food, medicines and other lifesaving medical supplies", and depriving Armenians in Nagorno-Karabakh of critical medical care.
It therefore ordered Azerbaijan to "take all measures at its disposal to ensure the unimpeded movement of persons, vehicles and cargo along the Lachin corridor in both directions."
Azerbaijan has denied any blockade, saying the activists are staging a legitimate protest against what it characterised as illegal mining activity.
The country's ministry of Foreign Affairs in a statement said it would "continue to uphold the rights of all people under international law and to hold Armenia to account for its ongoing and historic grave violations of human rights".
The court rejected a plea for provisional measures by Azerbaijan that would order Armenia to help remove land mines from areas it previously controlled, and to stop planting explosive devices which prevent Azeri nationals from returning to their former homes.
It also rejected pleas by Armenia to order Azerbaijan to stop alleged orchestration of protests and disruption of natural gas flows to Nagorno-Karabakh.
The court instead referred to the emergency measures it had issued in the tit-for-tat cases brought by the feuding South Caucasus neighbours in 2021, which ordered both countries to not do anything that would make the conflict worse and to prevent the incitement of racial hatred against each others' nationals.
The World Court in The Hague is the UN court for resolving disputes between countries.
Its rulings are binding, but it has no direct means of enforcing them.
Reuters