Separatist forces in the disputed region of Nagorno-Karabakh launched a counteroffensive and said they regained strategic high ground, as heavy fighting continued to rage between Azerbaijani and ethnic Armenian forces.
Azerbaijan, meanwhile, announced a unilateral cease-fire on April 3, a day after the fighting erupted in the South Caucasus mountain enclave, located within Azerbaijan itself.
It was the worst outbreak of violence in the two decades since a bloody ethnic conflict erupted into full-scale war and ended with ethnic Armenian separatists taking control of the territory in 1994.
At least 18 Armenian soldiers were reported killed a day earlier when Azerbaijani troops advanced with tanks and heavy artillery, officials said. The Azerbaijani side has announced 12 combat deaths.
Fighting on April 3 was described as fierce in the region's northeast and along the southernmost section of the “Line of Contact,” which effectively serves as a front line separating the opposing sides.
Officials with Nagorno-Karabakh separatist fighters said its soldiers pushed Azerbaijani forces back from “tactically important” positions near the northern village of Talish. The separatists also claimed they destroyed three Azerbaijani tanks and an armored personnel carrier in the south.
Azerbaijan’s military, however, rejected that claim, saying Armenia failed "to regain positions lost by it” on April 2. Officials also claimed as many as 10 Armenian tanks were destroyed in the April 3 fighting -- a report rejected by a spokesman for the ethnic Armenian fighters.
Azerbaijan’s Defense Ministry said later on April 3 that it was calling a unilateral cease-fire in response to calls from international organizations.
Yerevan, however, dismissed the announcement as an “information trick.” David Babayan, a spokesman for Nagorno-Karabakh’s ethnic leader, also dismissed the announcement, saying Azerbaijani operations were continuing.
Nagorno-Karabakh military officials later said they were ready to discuss the terms of a cease-fire but only in the context of “restoring former positions.”
WATCH: Residents of the Azerbaijani town of Terter said that shells hit their homes on April 2 as fighting flared in the disputed region of Nagorno-Karabakh. Terter is located close to the Line of Control. Heavy fighting was reportedly continuing for a second day on April 3. (RFE/RL's Azerbaijani Service)
RFE/RL correspondents in Nagorno-Karabakh said that ethnic Armenian forces have been reinforcing their frontline positions by calling up hundreds of reservists and deploying heavy artillery.
Hundreds of other Armenians, most of them veterans of the 1991-94 conflict, reportedly were heading to the front lines from Armenia, which is connected to Nagorno-Karabakh by a narrow strip of territory that crosses high mountain passes and deep river valleys.
A legacy of the Soviet breakup known as a “frozen conflict,” the dispute has seen sporadic, low-level fighting between the two sides ever since the 1994 cease-fire, but nothing of the scale that erupted on April 2.
The dispute has bedeviled regional and international leaders for years, with the United States, Russia, and France taking the lead in trying to reach a permanent settlement, and tamp down tensions.
Diplomats from the three nations, grouped together in what’s called the Minsk Group, said they would convene a full-meeting April 5 in Vienna to discuss the breakdown of the 21-year-old cease-fire.
Along with Georgia, Armenia and Azerbaijan sit astride a key transit corridor in the South Caucasus, where oil, gas, and other goods move from South and Central Asia toward Europe.
Russia maintains strong economic ties with all three nations, particularly with Armenia, though Moscow’s war in Georgia in 2008 and its recent actions in Ukraine have worried leaders in all three countries.
In another potentially worrisome sign, the president of Turkey, which shares deep cultural, religious, and linguistic ties with Azerbaijan, has vowed to "support Azerbaijan to the end."
Turkey has enforced a border blockade against Armenia proper since the war in the early 1990s, and Turkish and Armenian nationalists have repeatedly torpedoed efforts by Yerevan and Ankara to restore trade ties.
Fueled by windfall revenues from its Caspian Sea oil and gas reserves, Azerbaijan has gone on a military spending spree in the past decades, buying new weaponry and equipment from Russia and elsewhere.
That’s worried analysts, who fear Baku might try to preemptively take back Nagorno-Karabakh, whose loss remains an unhealed 21-year-old wound for many Azerbaijanis.
With reporting by Reuters, AFP, TASS, and Interfax