International powers are increasing deliveries of suspected military supplies to factions in Libya’s civil war, ignoring a poorly enforced UN embargo as the shattered country braces for a new round of fighting.

The United Arab Emirates, which is backing Khalifa Haftar, the warlord commander of the self-styled Libyan National Army, is thought to have sent more than 100 deliveries by air since mid-January, according to flight-tracking data.

Haftar launched an offensive in April 2019 aimed at capturing Tripoli, the capital and the seat of the UN-backed government of national accord (GNA). Frontlines have been largely static in recent months, with both sides unable to break a military stalemate.

Most of the suspect UAE flights leave military bases in the UAE, while some appear to depart from a base run since 2016 by the UAE in Eritrea, where an authoritarian regime is in charge and there is minimal international monitoring.

In all, the flights are thought to have carried about 5,000 metric tons of cargo into Libya in very large chartered transport planes that land at an airport close to Benghazi, Haftar’s coastal stronghold, or in western Egypt, from where their loads are thought to be trucked into Libya.

It is unclear what these shipments contained but they may have included heavier artillery as well as other arms and ammunition. Shelling from long-range artillery blamed on the LNA has recently hit the centre of Tripoli.

Experts say the cargos may also contain communications technology, spare parts, basic equipment and other non-lethal items necessary for fighting a war. Asked for a response to the flight-tracking data the UAE said it did not comment on military operations.

In addition to the support from the UAE and Egypt, Haftar has been backed by Saudi Arabia, Jordan and Russia. Many of the flights stop at Aqaba, the Jordanian port city.

Facebook Twitter Pinterest Supporters of Khalifa Haftar’s LNA in Benghazi celebrate on top of a Turkish military armoured vehicle, which the LNA said it confiscated during clashes in Tripoli. Photograph: Esam Omran Al-Fetori/Reuters

In December the Guardian reported that an influx of 3,000 Sudanese men had been sent to Benghazi to fight for Haftar, joining about 600 Russian mercenaries, in another sign the conflict’s parameters are growing.

The GNA is supported by Turkey, which has sent 2,000 fighters from Syria, and Qatar. Most of Turkey’s assistance travels by sea. Ankara says it intervened only when the level of weapons supplies provided to Haftar by his supporters meant the Tripoli government was in danger of falling.

Last month Italian authorities arrested the captain of a Lebanese-flagged cargo ship seized in the port of Genoa on suspicion of trafficking arms to Libya. The vessel, the Bana, was spotted by French warships operating in the Mediterranean not long before it reached Genoa on 2 February.

It was then blocked by police in Genoa harbour after a ship’s officer told Italian authorities that weapons had been loaded on to the Bana at the Turkish port of Mersin then transported to the Tripoli, a judicial source told Reuters.

The shipment included armoured vehicles, self-propelled artillery, mortars and anti-aircraft guns, Italian media reported.

The ship was originally scheduled to sail from Turkey to Genoa. But according to the informant, who has requested political asylum, Turkish military officers escorting the shipment had told the crew to declare that the stop in Tripoli was due to a mechanical problem. There are also claims of two further shipments in recent weeks.

Facebook Twitter Pinterest Bana, a Lebanese-flagged cargo ship, docked in the port in Genoa, in northern Italy on 20 February. Photograph: AP

The conflict began when Col Muammar Gadaffi was deposed in 2011 and has drawn in powers from across the region and beyond. Analysts fear intensified fighting in Libya will further destabilise north Africa and swell the flow of migrants into Europe.

Last month, rival military officials met in Geneva, where the UN said they agreed to a draft ceasefire agreement. The fate of the draft remains unclear. On Tuesday Haftar met German chancellor Angela Merkel in Berlin as part of a German effort to secure a lasting ceasefire.

The UN mission in Libya said in January numerous cargo and other flights were observed landing at airports in the western and eastern parts of the country, providing the parties with advanced weapons, armoured vehicles, advisers and fighters.

In February, the UN security council passed a resolution calling for enforcement of the arms embargo and a ceasefire. Russia abstained from the vote. Diplomats took this as a sign that Moscow might not be committed to a UN-led political mediation.

The UN’s inability to enforce an arms embargo, the continued fighting around Tripoli and the impasse in negotiations over a ceasefire led to the resignation of the UN special envoy for Libya, Ghassan Salamé, at the beginning of March.

He had been angered that the UN was not willing to back up its own officials and censure the widely known suppliers of arms in the civil war. Diplomatic divisions in the west over support for Haftar had also weakened him.

Facebook Twitter Pinterest Fayez al-Sarraj, the prime minister of Libya’s government of national accord, visits the port in the capital, Tripoli, after it was hit by rocket fire on 20 February. Photograph: Mahmud Turkia/AFP via Getty Images

The recently retired UN weapons inspector for Libya, Moncef Kartas, said there was “no respect for the UN arms embargo, absolutely none”. The UN deputy special envoy for Libya, Stephanie Williams, has described the UN arms embargo imposed on Libya as a joke.

The EU has agreed to deploy warships, planes and satellites to stop the flow of weapons into Libya, as the bloc winds down a military mission that had once rescued migrants and refugees from drowning in the Mediterranean.

A recent UN report accused Jordan, Turkey and the UAE of routinely and sometimes blatantly supplying weapons to their clients in Libya, “employing little effort to disguise the source”.