NATO Secretary-General Anders Fogh Rasmussen on Thursday said he was "deeply concerned" about the pardoning of a Azerbaijani soldier who axed an Armenian officer to death during a NATO training course.

"The act he committed in 2004 was a terrible crime and should not be glorified," Rasmussen said in a speech at Yerevan State University during a visit to Armenia.

Hundreds protested outside the Hungarian consulate in Yerevan on Saturday after Budapest sent a soldier who murdered an Armenian back to his native Azerbaijan, where he was immediately pardoned.

Several hundred angry demonstrators burned the Hungarian flag and threw eggs, tomatoes and coins, accusing Budapest of doing a deal with Baku in order to profit from Azerbaijan's energy riches.

As the passengers from battle-ravaged Aleppo disembarked at Yerevan's Zvartnots airport, tearful relatives gripped them tightly in emotional embraces.

"Thank God you've arrived safe and sound!" one cried out.

Armenian forces killed five Azerbaijani soldiers in a border clash Tuesday, in a new flaring of tensions as U.S. Secretary of State Hillary Clinton visits the volatile Caucasus region.

The Azerbaijani Defense Ministry said fighting broke out when "a group of Armenian saboteurs made an attempt to penetrate the military positions of the national army" in the country's north-west -- the second reported outbreak of deadly violence along the border between the ex-Soviet enemies this week.

Azerbaijani troops killed three Armenian soldiers on Monday during an alleged incursion attempt on the border between the enemy ex-Soviet states, the Defense Ministry in Yerevan said.

"On June 4, the Azerbaijani side once again roughly violated the ceasefire, attempting to penetrate Armenian positions," a ministry statement said.

Armenia's governing party on Monday won parliamentary elections seen as a test of the ex-Soviet state's fragile democracy but opposition leaders alleged violations and vowed protests.

European election observers from the OSCE praised the election process as competitive but said it had been undermined by a series of democratic failings including pressure on voters and an inadequate complaints process.

Armenians started voting on Sunday in parliamentary elections amid a battle for supremacy between the governing party and its coalition partner, led by a wealthy former arm wrestling champion.

"We expect highly active participation," Armen Khazarian, head of the commission at one polling station in Yerevan, told AFP.

More than 140 people were injured on Friday when gas-filled balloons exploded at a governing party campaign concert in the Armenian capital ahead of parliamentary polls on Sunday, officials said.

The emergencies ministry said 144 people suffered burns when scores of promotional balloons burst into flames at a concert staged by President Serzh Sarkisian's Republican party in Yerevan's central Republic Square.

Thousands of Armenians staged a procession to a hilltop memorial above the capital on Tuesday to mark the 97th anniversary of the genocide of their kin by Ottoman Turks during World War I.

From early morning, crowds of people joined the annual procession, carrying candles and flowers to lay at the eternal flame at the center of the monument commemorating the mass killings.

Turkey is ready to share the pain of Armenians as they prepare to mark the 100th anniversary of the Armenian genocide in 2015, Turkish Foreign Minister Ahmet Davutoglu has said.

"We want to share the pain of those who are ready to share it with us," Davutoglu was quoted as saying by Anatolia news agency in an interview with state-run television TRT Haber late Tuesday.