Convoys of diplomatic vehicles criss-crossed the rainswept Swiss city, with journalists trying to work out who was going where, as the countries involved kept tight-lipped on how the talks were progressing.

Though the neutral ground of Geneva is well used to hosting international negotiations on the world's most pressing topics, two sets of such talks on the same day is an exceptional sight.

Early Tuesday, reporters and camera crews positioned themselves opposite the five-star Intercontinental Hotel, hoping to spot the Ukrainian, Russian and US delegations arriving for the first of two days of intense negotiations.

Meanwhile across Lake Geneva, other journalists were in the ultra-plush Cologny district, hoping to catch US and Iranian delegations arriving for talks being held at the Omani's ambassador's residence.

Journalists crammed onto the sidewalk by the neatly clipped hedgerows opposite the private street leading to the residence, to the bemusement of passing joggers and delivery drivers.

- Scrum in the swanky suburbs -

As the Iranian motorcade left, demonstrators shouted "terrorists!" and surged forward throwing objects, with the police swiftly shoving them -- and the reporters behind -- backwards, as some tumbled over in the melee.

Demonstrators voiced their outrage over what rights group say is the killing of thousands of Iranian protesters by security forces in the Islamic republic.

"They are killing children, they are killing teenagers by the thousands," protester Hossein, an Iranian living in Switzerland, told reporters.

"Why do you keep negotiating with terrorists?

"Regime change in Iran is the only way. Regime change by the people of Iran."

With scant information given by the various sides, back at the Intercontinental, vehicle registration plates gave away that the US delegation was sweeping in, straight from the Iran talks.

The luxury hotel is a favourite with the diplomatic jet-set, given its proximity to the United Nations, and is well-versed in hosting sensitive talks behind closed doors.

Across the street, organisers erected pop-up tents behind temporary barricades, offering the ever-growing media crowd some shelter from the frequent downpours.

With countries' diplomatic missions giving little away, journalists tried their luck approaching official-looking types in the hope of extracting nuggets of information. Some turned out to be bystanders who happened to be smartly dressed.

- Hope against hope -

Outside the United Nations, around 200 demonstrators denounced Iran's deadly protest crackdown, holding placards reading: "No negotiations with murderers".

They were later replaced by around 100 pro-Ukraine activists denouncing Russia's nearly four-year-old invasion, brandishing banners reading "Stop killing Ukrainians!" and "Save Ukraine to preserve peace in Europe".

Alexandre Plautard, a 24-year-old international relations student, said: "This is a historic moment. We might finally have a way forward."

He came to "remind the world of Russia's cruelty to Ukrainians", with its strikes on energy infrastructure during the bitter winter.

However, the Russians ultimately "have no interest in peace", he told AFP.

Psychology student Marianne, a Ukrainian who arrived in Geneva in 2022, said: "We are desperate. We don't really believe them (the Russians), but we hope there will be changes.

"We don't want to be too positive so as not to be disappointed."