Anti-government protests are spreading across Iran following the military’s admission of responsibility for the downing of a Ukraine-bound passenger jet.

Thousands of demonstrators have defied “a heavy security presence” to hold vigils in Tehran, where witnesses say police have used tear gas and “live rounds” to break up crowds, The Guardian reports.

The city’s police chief has denied the alleged use of live ammunition, claiming that officers have been ordered to “show restraint”.

Is the US-Iran diplomatic crisis worsening?

The US assassination of Iranian General Qasem Soleimani earlier this month triggered protests against the Donald Trump regime in Tehran and other cities across the Islamic republic.

However, after the Iranian Revolutionary Guard Corps last week admitted firing the missiles that downed Ukraine International Airlines Flight 752, killing all 176 people on board, public anger has turned against Iran’s own government.

Chants of “death to America” have been drowned out by those of “death to the dictator”, as protestors direct their ire at Supreme Leader Ayatollah Ali Khamenei, reports Reuters.

A total of 82 Iranians were on board the Ukraine-bound flight shot down shortly after take-off from Tehran’s Imam Khomeini International Airport on 8 January.

According to The Daily Telegraph’s Middle East correspondent Raf Sanchez, the government has now moved to deny the military’s original confession, claiming that Iran did not shoot down the plane.

Rouhani government spokesman: "All relevant authorities had assured us that there had been no missile involved in the downing of the Ukrainian plane." i.e. accusing the Revolutionary Guard of misleading them over what happened to #PS572 — Raf Sanchez (@rafsanchez) January 13, 2020

The denial has been widely interpreted as an attempt to de-escalate the anti-government protests, which Reuters describe as a “new challenge to [Iran’s] rulers” that could cause a “legitimacy crisis” among the country’s clerical leadership.

Tensions with the West have also soared once again, after the British ambassador to Tehran was briefly detained at a vigil for the plane victims. The Iranian authorities have criticised Robert Macaire for joining the crowds in the capital, amid claims that he has been inflaming the anti-regime demonstrations.

On Sunday, hard-line religious students and regime supporters burned the Union Flag outside the British Embassy in Tehran while chanting “death to England”, The Times reports.

Meanwhile, President Trump has tweeted his support for the protestors, and warned the authorities to “stop the killing of your great Iranian people”.

To the leaders of Iran - DO NOT KILL YOUR PROTESTERS. Thousands have already been killed or imprisoned by you, and the World is watching. More importantly, the USA is watching. Turn your internet back on and let reporters roam free! Stop the killing of your great Iranian people! — Donald J. Trump (@realDonaldTrump) January 12, 2020

Tensions had briefly appeared to be easing following the Trump-ordered assassination of Soleimani in Iraq. The US leader suggested last week that Iran was “standing down” after carrying out retaliatory attacks on Iraqi air bases housing American troops.

Relations between Washington and Tehran have been strained since 2018, when Trump announced the US withdrawal from the nuclear deal brokered in 2015 by then-president Barack Obama. An independent US report released following the withdrawal warned that the stage had been set for an all-out war - with President Trump’s decision to surround himself with hardliners in his administration increasing the risk.

As The Independent reported at the time, Israel and Saudi Arabia - the two states that successfully lobbied Trump to sabotage the nuclear agreement - “have long urged Washington to take military action against Iran”.

While the threat of conflict is growing more real, the BBC’s defence and diplomatic correspondent Jonathan Marcus has said that “it is important both not to overstate nor to understate the significance of the moment”.

Marcus highlights that Russia and China are not yet “key players” in the drama, meaning that a global conflict is not set to break out imminently, but that “a significant Iranian retaliation is to be expected”.

Tension between the US and Iran is also not the only dispute that could trigger international conflict.

UK-Iran tanker wars

The UK has also recently had a diplomatic run-in of its own with Iran, after Tehran attempted to prove its military might in the Strait of Hormuz, says The Independent.

Iran’s seizure of the Stena Impero in the Gulf last summer came weeks after Britain helped seize oil tanker Grace 1 off Gibraltar. The UK government claimed the Iranian vessel was transporting oil to Syria, in violation of EU sanctions.

Then-foreign secretary Jeremy Hunt described Iran’s retaliatory seizure as an illegal move, deeming it “utterly unacceptable”.

In footage released by the Iranian government in July, armed troops wearing ski masks are seen rappelling onto the British tanker’s deck from a helicopter hovering overhead.

The broadcaster added that Iran appeared to be sending two clear messages to the UK: “we want our tanker back” and “look at what we can do in the Persian Gulf. Do you want more?”

South China Sea

Tensions are also rising in the South China Sea between the US and China. Beijing views the expanse off the coast of East Asia as sovereign territory, while Washington regards “China’s militarisation of the area as a transparent rewriting of the international rules”, says The National Interest.

“Neither side is backing down - nor does either country seem interested in a compromise,” the US magazine adds.

During an interview in November, Vice President Mike Pence was asked about China’s failure to meet US demands over unfair trade practices, political interference and military manoeuvres in the region. Pence’s response: “Then so be it... We are here to stay.”

Confrontation in the region is all but “inevitable”, says Maochun Yu, a history professor at the US Naval Academy, in Maryland.

Beijing is trying to push out its borders and expand control of peripheral waters. “China’s geopolitical and geostrategic priority is to revise or change the existing international order that has been based upon a complex system of rules, laws and customs that govern various global commons including the South China Sea,” he told Foreign Policy.

Threat of Russia to Europe

Rising tensions between Russia and Ukraine reached boiling point in October 2018, when Ukraine’s then-president Petro Poroshenko voiced his concerns about a possible “full-scale war” with Russia following the seizure of three of Ukraine’s naval ships in the Azov Sea.

The Guardian reports that after opening a bridge across the Kerch Strait, Russia has gradually brought the entire area under its control, causing “severe economic damage” to Ukrainian trading ports.

This domination, combined with Russia’s previous advances in eastern Ukraine, have prompted calls for the West to respond.

The head of the British Army, General Mark Carleton-Smith, told The Telegraph: “Russia today indisputably represents a far greater threat to our national security than Islamic extremist threats such as al-Qa’eda and Isis.”