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.

Azerbaijan foiled an attempt to stage "terrorist" attacks while it was hosting the Eurovision Song Contest last week and arrested dozens of suspected plotters, the security ministry said Wednesday.

"The main goal of the group was to stage terrorist acts in Baku during Eurovision," the National Security Ministry said in a statement. "As a result of the measures taken, 40 members of the group were arrested."

Investigators working in four countries have amassed new evidence linking attempts to assassinate officials and businessmen to either Hizbullah or Iran-based operatives, The Washington Post reported Monday.

Citing unnamed U.S. and Middle Eastern security officials, the newspaper said the evidence included phone records, forensic tests, coordinated travel arrangements and even cellphone SIM cards purchased in Iran and used by several of the would-be assailants.

Iran has recalled its ambassador to Azerbaijan for consultations, the Iranian embassy in Baku said on Tuesday, amid a growing row between the two neighbors.

"Ambassador Mohammad Bagher Bahrami left for Tehran on May 21 in connection with the insulting of religious saints in Azerbaijan. He was recalled for consultations," charge d'affaires Ahmed Nemati said in a statement.

Azerbaijan's security forces arrested 17 alleged Islamist militants in a nationwide operation Friday in which a security service officer and an alleged extremist were killed, authorities said.

The National Security Ministry "arrested 17 members of an illegal armed group which were planning subversive and terrorist acts aimed at undermining political stability in the country," the ministry said in a statement.

Iran on Saturday formally protested against an accusation by Azerbaijan that it ordered "terrorist acts" in the neighboring republic against Western and Israeli targets.

Azerbaijan's ambassador to Tehran, Javanshir Akhundov, was summoned to the foreign ministry to hear an official denial that Iran was involved in plots Baku claimed were masterminded by Iran's Revolutionary Guards, the state news agency IRNA reported, quoting a ministry statement.

Azerbaijan has arrested 22 people on suspicion of plotting attacks on the U.S. and Israeli embassies in Baku on behalf of neighboring Iran, the national security ministry said Wednesday.

"Twenty-two citizens of Azerbaijan have been arrested by the national security ministry for cooperating with the Iranian Sepah," its statement said, referring to the elite Iranian Revolutionary Guards.

Azerbaijan on Monday rejected as "slander" Iranian claims that Baku has been collaborating with Israel's spy services and helping assassins who have killed Iranian nuclear scientists.

The Azerbaijani foreign ministry condemned a protest note given to its ambassador in Tehran which complained about the alleged collaboration. The note demanded that Baku prevent Mossad from carrying out anti-Iranian "activities" on its soil.

Police in Azerbaijan have detained two people accused of plotting attacks on prominent foreigners masterminded by a man with alleged links to Iranian intelligence, officials said Thursday.

The two Azerbaijani citizens "were making preparations for the assassination of public figures who are foreign nationals ... that is, preparing to commit a terrorist act", the national security ministry said in a statement.