YEREVAN/BAKU－Armenia and Azerbaijan accused each other on Monday of attacking civilian areas on a ninth day of fighting, the deadliest in the South Caucasus region for more than 25 years.

Hundreds of people have been killed in the latest outbreak of war over Nagorno-Karabakh, a mountainous region.

Nagorno-Karabakh said Azerbaijani forces launched rocket strikes on its capital Stepanakert, while Azerbaijan said Armenia fired missiles at several towns outside the region.

"The enemy is firing rockets at Stepanakert and Shushi. The Defense Army response will not be long in coming," said Vahram Pogosyan, a spokesman for the Nagorno-Karabakh leader.

"Tense fights are in progress," said Armenian Defense Ministry spokeswoman Shushan Stepanyan.

Azerbaijan said that Armenia had been launching missile attacks against densely populated areas and civilian infrastructure in Azerbaijan. The Azerbaijani defense ministry said its radar system recorded that launches were made from the territory of Armenia.

Artrsun Hovhannisyan, an Armenian defense ministry official, said it was "fake and complete misinformation" that Armenia opened fire on Azerbaijani strongholds.

The clashes are the worst since the 1990s, when nearly 30,000 people were killed, and are spreading beyond the Nagorno-Karabakh region. They have raised international concern about stability in the South Caucasus, where pipelines carry Azerbaijani oil and gas to world markets.

Moscow urges truce

The conflict threatens to drag in other regional powers as Azerbaijan is supported by Turkey, while Armenia has a defense pact with Russia.

On Sunday, Azerbaijani President Ilham Aliyev demanded that Armenia set a timetable for withdrawing from Nagorno-Karabakh and surrounding Azerbaijani territories, and said Azerbaijan would not cease military action until that happened.

Russian Foreign Minister Sergei Lavrov called for an immediate cease-fire in a telephone call with his Armenian counterpart Zohrab Mnatsakanyan.

Lavrov reaffirmed Moscow's readiness to assist the parties in returning the Nagorno-Karabakh settlement process to the political and diplomatic channels under the auspices of the Organization for Security and Cooperation in Europe, or OSCE, Minsk Group in accordance with the joint statement of the presidents of Russia, the United States and France.

On Thursday, Russian President Vladimir Putin, US President Donald Trump and French President Emmanuel Macron, representing the OSCE Minsk Group cochair countries, called in a joint statement for an immediate cessation of hostilities between countries involved in the armed conflict in the Nagorno-Karabakh region.

Azerbaijan, however, says it has lost patience with the OSCE's failure to resolve the conflict.