YEREVAN, Armenia (AP) — The Azerbaijani army closed in Thursday on a key town in Nagorno-Karabakh following more than a month of intense fighting, while top diplomats from Azerbaijan and Armenia prepared for more talks to try to end their long conflict over the separatist territory.

Nagorno-Karabakh’s separatist leader, Arayik Harutyunyan, said Azerbaijani troops had advanced to within 5 kilometers (about 3 miles) of the strategically placed town of Shushi. He urged residents to mobilize all their resources to fend off the attack.

“The one who controls Shushi controls Nagorno-Karabakh,” Harutyunyan said in a video address from the town's cathedral, which was severely damaged by Azerbaijani shelling this month. “We must realize that and take part in defending Shushi. We must reverse the situation.”

Shushi is located about 5 kilometers south of Nagorno-Karabakh's regional capital, Stepanakert.

Nagorno-Karabakh lies within Azerbaijan but has been under the control of ethnic Armenian forces backed by Armenia since a war there ended in 1994.

The latest fighting began Sept. 27 and has involved heavy artillery, rockets and drones, in the largest escalation of hostilities over the separatist region in the quarter-century since the war ended. Hundreds and possibly thousands of people, have been killed in a little over a month.

Separatist authorities of Nagorno-Karabakh accused Azerbaijani forces Thursday of shelling Stepanakert, Shushi and Martakert with Smerch multiple rocket systems, a devastating Soviet-designed weapon intended to ravage wide areas with explosives and cluster munitions. Martakert was also raided by Azerbaijani aircraft, officials said.

Azerbaijan's Defense Ministry denied using aviation and accused Armenian forces of shelling the Terter, Goranboy and Barda regions of Azerbaijan. One civilian was killed in the Goranboy region, according to Hikmet Hajiyev, a foreign policy advisor to the Azerbaijan's president.

The ministry also reported downing two Armenian Su-25 warplanes, a claim Armenian officials rejected as “disinformation.”

According to Nagorno-Karabakh officials, 1,166 of their troops and 39 civilians have been killed in the clashes so far. Azerbaijani authorities haven’t disclosed their military losses, but say the fighting has killed at least 90 civilians and wounded 392.

Russian President Vladimir Putin said last week that, according to Moscow’s information, the death toll from the fighting was nearing 5,000, a significantly higher number than officially reported.

The hostilities have raged for a fifth week despite international calls for peace and three attempts at establishing a cease-fire. The latest U.S.-brokered truce frayed immediately after it took effect Monday, just like two previous cease-fires negotiated by Russia. The warring sides have repeatedly blamed each other for violations.

Russia, the United States and France have co-chaired the so-called Minsk Group set up by the Organization for Security and Cooperation in Europe to mediate in the conflict, but they have failed to score any progress.

The Minsk Group’s co-chairs were set to meet with the foreign ministers of Azerbaijan and Armenia in Geneva on Thursday, but the negotiations were pushed back until Friday and the prospects for a breakthrough appeared dim.

Armenian Foreign Ministry spokesperson Anna Naghdalyan said the change of date was “linked to the evolving situation and logistical issues,” adding that negotiating a lasting and verifiable cease-fire is a priority for Armenia.

Azerbaijani President Ilham Aliyev has repeatedly criticized the Minsk Group for failing to achieve any results in three decades and insisted that Azerbaijan has the right to reclaim its territory by force since international mediation has failed.

Speaking Thursday at an investor conference in Moscow, Putin said that negotiating a settlement for the decades-long conflict is extremely challenging.

“It's a tight knot, and there are no simple solutions,” Putin said. “Each side has its own truth.”

Russia, which has a military base in Armenia and a security agreement to protect its ally, has been involved in a delicate diplomatic act while trying to also maintain good ties with Azerbaijan and to avoid a showdown with Turkey.

Before the latest escalation of hostilities, Russia proposed a peace plan that would see Azerbaijan reclaim control of several of its regions outside Nagorno-Karabakh that Armenian forces captured during the war that ended in 1994. In exchange, Nagorno-Karabakh would be given security guarantees and a crippling blockade of Armenia by Turkey and Azerbaijan would be lifted.

Armenia has resisted the plan.

Residents of Nagorno-Karabakh, whose homes have been damaged by shelling, also appeared to have little faith in the international peace efforts.

“Neither France nor Russia are doing anything. We are left alone,” Vovik Zakharian, a resident of Shushi, a town that came under repeated shelling, said.

Zakharian, 72, inspected his apartment Thursday after it was damaged in morning strikes.

"We will fight till the end," he said. “We have to try our best.”

___

Associated Press writer Daria Litvinova and Vladimir Isachenkov in Moscow and Aida Sultanova in London contributed to this report.