Moscow -- Two dozen Ukrainian sailors taken prisoner by Russia when it seized three Ukrainian navy ships in November, have appeared in a Moscow court for the first time, as Ukraine said their trial violates the Geneva Conventions.

The 24 sailors were captured when Russian coast guard vessels fired on and then boarded their three small Ukrainian ships in the Black Sea close to Crimea in late November, setting off a major international crisis.

Russia impounded the Ukrainian ships and is now placing their crews on trial, charging them with border violations. Ukraine and Western countries have accused Russia of violating international law and have demanded their release. President Donald Trump cited the sailors’ detention when he canceled a planned meeting with Russia’s president Vladimir Putin at the G20 summit in December, saying he could not sit down with Putin until they were let go.

On Monday, the sailors were led into Moscow's Lefortovsky district court in groups by masked Russian officers wearing camouflage, some armed with assault rifles. The men have been held in the city's Lefortovo prison since they were transferred from Crimea in late November and Monday’s hearing was an effort by prosecutors to extend the sailors' pretrial detention.

Ukraine officials have said the sailors should be treated as prisoners of war and, on Monday, their lawyers said Russia was violating the Geneva Convention by trying them as civilians. The court rejected a motion by the men’s lawyers to move the trial to a military court. In multiple hearings on Monday, the judges ordered the pretrial detention of at least 20 of the sailors be extended until April 26.

We’re warriors for our country.

A group of the men’s relatives were brought in by Ukraine’s government to attend, and the families' waited tearfully for hours outside the courtrooms where they were, for the most part, only permitted to enter the courtroom for the final ruling. Some of the men’s mothers and relatives applauded the men as they were brought in and out of the courtrooms.

In a sign of the case’s international significance, about a dozen diplomats from Western countries including a United States embassy official were present, whose attendance was intended to signal solidarity with Ukraine.

The incident in November was a serious escalation of the four-year conflict between Russia and Ukraine that began when Russia invaded Crimea in 2014. It sparked fears that the detentions could lead to the return of full-scale war and prompted Ukraine's government to temporarily impose martial law in some regions.

Everyone is doing politics and the people suffer.

On November 26, the three Ukrainian ships -- two small gunboats and a tug -- were blockaded by Russian vessels as they tried to pass through the Kerch Strait, a narrow stretch of water separating Crimea from mainland Russia. The Ukrainian boats had been headed for Mariupol, a Ukrainian-controlled port located in the Sea of Azov beyond the strait. After a stand-off, the Russian ships rammed and eventually opened fire on the Ukrainian boats, before boarding them. Six Ukrainian servicemen were hurt in the assault.

Russia has claimed the Ukrainians' passage was a deliberate provocation and accused them of flouting standard procedure for passing through the strait by not accepting a Russian pilot ship. But Ukraine has accused Russia of mounting a deliberate attack on its ships and violating their right -- backed by international law -- to pass freely through the strait.

The dispute is a product of Russia’s 2014 annexation of Crimea. A 2003 treaty guarantees equal access to the Kerch Strait, but after it seized Crimea, Russia has sought to exert greater control over the waterway. The situation worsened after the Kremlin built an 11-mile bridge spanning the strait, with Ukraine accusing Russia of imposing a partial blockade.

The United States, the European Union and the North Atlantic Treaty Organization have backed Ukraine. The U.S. embassy in Kiev on Monday called on Russia to immediately release the sailors and "not use them as political pawns."

For Lyubov Chuliba's son, Sergey Chuliba, this is the second time he has been caught up in the conflict over Crimea. In 2014 during Russia’s invasion he was serving at a Ukrainian military base in Crimea when it was surrounded by unmarked Russian troops. Offered an ultimatum to defect, Chuliba refused, choosing to eventually evacuate with thousands of other Ukrainian personnel.

Alena Bezyazichniy’s son, Yuri, was aboard the Ukrainian gunboat that was fired on -- the Berdyansk. Her husband was killed while fighting Russian-backed separatists near the town of Avdeevka in eastern Ukraine, she said. Now her son is going on trial in Russia.

“We’re warriors for our country,” Bezyazichniy said.

Chuliba and Bezyaichniy waited for six hours at the door of the courtroom. When the group with their sons were finally brought to the court building by masked officers, the two women threw themselves onto them, smothering them with kisses before they were taken into the courtroom.

Chiluba’s father, Roman, said the men were worried about a young dog they had been raising on their captured boat. He discretely dabbed his eyes after his son was brought through.

“Everyone is doing politics and the people suffer,” said Roman, 62,

In court, the men refused to say anything other than their name and rank, citing Geneva Conventions guidelines that protect soldiers from having to divulge more.

One of the men’s lawyers, Ilya Novikov said Russia was violating the Geneva Conventions by refusing to treat the men as POWs, noting they had been captured in a serious military incident. He said the Ukrainian position was backed by Article 2 of the Geneva Conventions -- which stipulates that countries are bound by the treaties even when one of them does not recognize they are engaged in a state of war.

Russia, though, now seems determined to treat the captured sailors’ case as a mundane criminal trial, he said.

“It is already decided on some very top level that these people will be regarded as common criminals,” Novikov told reporters. He said the court’s decisions were being dictated by senior Russian government officials.

Ukrainian officials have expressed hope the sailors might be traded in a prisoner exchange. Novikov said he was optimistic that international pressure and the threat of fresh sanctions could force Russia to eventually to make a deal over the men.

Putin suggested in his end-of-year press conference in December the possibility of a prisoner exchange for the men, but noted it was “too early” to discuss and said it could only be raised once the men had been tried.