Turkey and Armenia on Saturday signed landmark pacts to normalise their relations and open their shared border, a first step to reconciliation after decades of hostility over World War I-era massacres.

But the signing attended by top European and US officials did not go as smoothly as planned, with the ceremony delayed by an apparent dispute over statements the two sides were to make afterward, causing them to be scrapped.

Armenian Foreign Minister Edouard Nalbandian and his Turkish counterpart Ahmet Davutoglu shook hands after signing the two protocols in a ceremony at the university in the Swiss city of Zurich.

But the two ministers and US, Russian, French and Swiss counterparts immediately left the room instead of making their scheduled statements in a deal to bypass the problems that caused the three-hour delay, US and Turkish diplomats said.

"Political passions are running high" on both sides, a US official said.

Relations between NATO member Turkey and Russian-backed Armenia have been cut since the World War I massacres of Armenians under Ottoman rule.

The bridge-building by the two governments after more than a year of discrete Swiss-mediated talks is still hampered by fierce opposition from critics at home, as well as within the influential Armenian community abroad.

The protocols still have to clear the hurdle of parliamentary ratification in each country before they can take effect.

US State Department spokesman Ian Kelly told reporters that the ceremony was delayed after "a last minute hitch" with the Armenians, touching off frenetic scenes in the northeastern Swiss city.

More than two hours after the scheduled ceremony, the Armenian foreign minister and US Secretary of State Hillary Clinton finally arrived at the university, after diplomatic efforts by US and Swiss mediators to resolve the hitch.

Together with EU foreign affairs chief Javier Solana, Russian Foreign Minister Sergei Lavrov and French Foreign Minister Bernard Kouchner, Clinton was aiming to provide a public show of support for the Turkish-Armenian deal. "No problems, they signed," Kouchner said afterwards, brushing off the extraordinary events of the evening.

An AFP reporter was in Clinton's convoy when it unexpectedly turned around while travelling to the venue and rushed back to a hotel where she had earlier held bilateral talks with the Turkish and Armenian ministers.

US Assistant Secretary of State for European and Eurasian affairs Phil Gordon met Nalbandian at the hotel to try to iron out Armenian concerns about statements to be made during the ceremony, officials said.

Clinton later huddled with diplomats in her limousine parked outside the hotel, while a Turkish diplomat was shuttled there in a police car with sirens blaring.

The two protocols establish diplomatic ties, set up regular dialogue including on their emotionally-charged history, and open the Armenian-Turkish border, a US official said.

Observers say official reconciliation could allow landlocked Armenia to gain a much-needed economic boost, while Solana underlined that it would have an important impact on Turkey and Armenia's relations with the EU.

The European Union welcomed the deals, saying they would ease tensions in the southern Caucasus.

Although the Turkish and Armenian governments can command parliamentary majorities, the domestic climate prevents them from rushing ahead with ratification by lawmakers.

Armenian President Serzh Sarkisian said in a nationwide address Saturday that Armenia has "no alternative to establishing ties with Turkey without preconditions."

Up to 10,000 people took to the streets of the Armenian capital Yerevan on Friday to protest against the creation, under the deal with Turkey, of a commission to study the Ottoman-era massacres of Armenians.

Critics believe the step calls into question Armenian claims of genocide in 1915-1917, when they say 1.5 million of their kinsmen were systematically killed by Ottoman Turks.

Turkey denies the claims and says the death toll is inflated, having shunned diplomatic ties over Yerevan's campaign to have the killings recognised internationally as genocide.

Another long-running dispute over Nagorny-Karabakh -- an Armenian-majority enclave which broke free from Azerbaijan after a war in the early 1990s -- is also weighing on reconciliation efforts.

Turkey closed its border with Armenia in 1993 to support Azerbaijan and the Turkish government has been accused at home of making concessions that would sell out Azerbaijan.