At least five Armenian civil society activists have been attacked by unidentified assailants while taking part in recent protests in the capital Yerevan, Human Rights Watch said on Thursday.

"A spate of violent attacks against peaceful protesters appears to be a concerted effort to intimidate activists and should be effectively investigated," the New York-based rights group said in a statement.

Thousands flocked on Wednesday to a hilltop memorial above Yerevan to mark the 98th anniversary of the mass killings of Armenians in the Ottoman Empire during World War I which Armenia wants recognized internationally as a genocide.

In the annual ceremony broadcast by all national television channels, huge crowds headed to the memorial that commemorates the massacres to lay flowers at the eternal flame.

An unknown attacker shot and wounded a prominent candidate in Armenia's presidential elections, rocking the ex-Soviet state less than three weeks before it goes to the polls, police said Friday.

Paruyr Hayrikyan, head of the Union for National Self-Determination, is one of Armenia's best known politicians and a veteran figure who was jailed in Soviet times and then exiled for his promotion of Armenian independence.

A cargo plane that crashed at Brazzaville airport killing at least 27 people belonged to the Armenian freight specialist airline Rij Airways, the foreign ministry in Yerevan said Saturday.

The plane, carrying seven crew members, crashed as it tried to land in a storm on Friday.

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.

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.

President Michel Suleiman travelled to Armenia on Thursday on a three-day official visit that will include the signature of several cooperation agreements.

Suleiman left Rafik Hariri international airport along with First Lady Wafaa and a delegation of ministers and MPs on Thursday morning.

An Armenian soldier was shot dead by an Azerbaijani sniper on the frontline in the disputed region of Nagorny Karabakh on Saturday, the separatist Karabakh defense ministry said.

"Nineteen-year-old conscript Aren Simonian died because of enemy sniper fire," the ministry said in a brief statement.

Armenia's top chess players, lauded as heroes after winning the 2011 World Team Chess Championship this week, vowed on Friday to boost the small chess-mad country's status in the game even further.

The team's head coach said that future successes will be secured through official support and an unusual new scheme to promote the game among schoolchildren initiated by Armenian President Serzh Sarkisian, a keen player who also heads the country's Chess Federation.