Armenians Attack Karabakh City : Ethnic warfare: Fierce street battles are reported in Shusha, an Azerbaijani stronghold. Meanwhile, a cease-fire is signed in Tehran.

MOSCOW —  In a sudden switch in strategy, Armenians backed by tanks launched a full-scale assault Friday on the last major Azerbaijani stronghold in war-racked Nagorno-Karabakh, even as Armenian and Azerbaijani leaders shook hands in Iran on a cease-fire.

Fierce street battles were reportedly raging for mastery of Shusha as night fell. The Armenians claimed to have extinguished resistance in all but the southernmost districts of the hilly city; a spokesman for the Azerbaijani Popular Front said that the attack failed.

Many dead and wounded were reported on both sides, but no authoritative casualty figures were immediately available. Azerbaijanis said Shusha was subjected to a massive softening-up bombardment from 30 Armenian positions before the troops and at least four tanks went in.

“Many Azeris have already been killed, among them servicemen of the National Army and peaceful people,” the Assa-Irada press agency of Azerbaijan reported, quoting the Popular Front. The agency added that trucks trying to evacuate wounded were ambushed and fired on “point-blank.”

In Yerevan, Armenia’s capital, the Dashnaktsutyun nationalist party said eight Armenian fighters had been killed and more than 80 injured. “We are confident that by the morning, Shusha shall fall,” a spokeswoman said. “But we are afraid that after the fall of Shusha, fighting will begin in earnest along the whole (Azerbaijani-Armenian) border.”

The Interfax news agency said 1,000 armed Armenians supported by dozens of armored vehicles, heavy tanks and two military helicopters, were taking part in street battles. Simultaneously, the agency said, Armenians attacked the nearby city of Kosalar and brought the only evacuation route out of Shusha under fire.

Since early 1988, Armenians and Azerbaijanis have been feuding for control of Nagorno-Karabakh, a predominantly Armenian enclave inside Azerbaijan. In February, Armenians drove the Azerbaijanis out of their second-largest settlement there, Khojaly, in a slaughter that witnesses said cost the lives of at least 100 civilians.

On Friday, there seemed to be a glimmer of hope for an end to the four-year-old conflict when Armenian President Levon Ter-Petrosyan and Azerbaijan’s acting president, Yagub Mamedov, signed a cease-fire agreement in the Iranian capital of Tehran.

Iranian radio said the Tehran-brokered cease-fire would go into effect within a week and would be monitored by envoys from Iran and the Conference on Security and Cooperation in Europe (CSCE).

According to the radio, Ter-Petrosyan said, “after signing this document, both sides must use all their influence for establishing peace.”

Nagorno-Karabakh, which claims independence, has in the past refused to be bound by agreements between Armenia and Azerbaijan. Thus, the Azerbaijani news agency Turan was skeptical Friday, saying past cease-fire accords had been “no more than historical documents in politicians’ safes.”

A CSCE mission was supposed to land Friday in Nagorno-Karabakh’s capital, Stepanakert, but failed to fly in when Armenian officials said they could not guarantee the Europeans’ security. The delegation cooled its heels in a cellar in the Azerbaijani city of Agdam, riding out shellfire that the Azerbaijani Interior Ministry said killed three people and injured 20.

Leaders of the ethnic Armenian community in Nagorno-Karabakh say Stepanakert has been subjected to a recent firestorm of Azerbaijani shells and rockets that has made living conditions unbearable.

The Pro Armenia news agency reported that the territory’s Defense Council decided at a Thursday night meeting to switch from a defensive strategy to an offensive one by overrunning all batteries used to bombard Stepanakert.

The offensive began Friday morning when the Armenians destroyed an artillery position in the village of Jangasyan and captured a Grad multiple-rocket battery, the Interfax news agency reported.

Meanwhile, in the former Soviet Central Asian republic of Tajikistan, people observed a day of mourning for victims of violent political clashes earlier this week, but the question of who is now in charge seemed murkier than ever.

President Rakhman Nabiyev, a onetime Old Guard Communist party leader, was reportedly sequestered in the building of the former Tajik KGB.

In a televised interview, Nabiyev said he seeks a democratic, secular state for his republic, seemingly ruling out the participation of Muslim clerics in a new coalition government, as some opposition circles wanted.