BRUSSELS (AFP) - The search grew increasingly desperate on Thursday (March 24) for loved ones still missing after the Brussels attacks as relatives and friends clung to fading hopes of hearing good news.

Tuesday's attacks at Brussels airport and at a metro station in the Belgian capital killed 31 people and injured 300, 61 of whom were in critical condition.

Officers from the Belgian federal police's disaster victim identification team were working at the sites of both attacks, poring over the remains in a grisly process.

The task of identifying the dead was painstakingly slow, with names only gradually emerging, complicated by the violence of the explosions and because many of them are foreigners, police told RTBF television.

The victims came from across the world, reflecting the cosmopolitan nature of Brussels, Europe's symbolic capital.

Belgian Foreign Minister Didier Reynders has said around 40 nationalities were among the dead and wounded.

They include citizens of countries including Britain, Colombia, Ecuador, France, Germany, Hungary, Portugal, Romania, Spain and the United States.

A Facebook page where worried relatives, friends and colleagues can post notices of the missing has been set up. Pictures uploaded showed men and women, young and old, from Belgium and across the globe.

They have been shared thousands of times as people try to spread the word in the hope of finding out what happened to them.

"HAVE YOU SEEN THIS GIRL? Her name is ALINE BASTIN, Belgian, 29 years old. She was most probably on the metro," read one.

"We are DESPERATELY looking for her - should you have any news, PLEASE give a sign!" Chandrasekar Ganesan was looking for his brother Raghavendran.

"I have talked with people from Indian Embassy, Brussels and they told me that they are searching for him. They have also looked into many hospitals it seems but still there is no word of him," he wrote.

"Any leads would be really helpful." New York siblings Sascha and Alexander Pinczowski were at the airport. A Dutch newspaper said they were on the telephone to a relative when the bombs went off and the line went dead.

There has been no news of them since.

US couple Justin and Stephanie Shults had dropped off her mother at the airport when the blasts struck. They have not been heard of since.

"We are thankful for the outpouring of love and support we have received at this difficult time and ask for prayers for Justin and Stephanie," their family said in a statement.

David Dixon, 51, a British computer programmer who lived in Brussels, texted his aunt after the airport blasts to say he was safe.

But his family now fear he was caught up in the metro attack on his way to work, according to media reports.

One missing notice for a man who was at the airport said: "We are still looking for Andre Adam.

"His wife has been found, she's at hospital but we have no news about him." A young German couple who were married last year and headed for a New York holiday were waiting at the American Airlines check-in counter when when the suicide bombers struck, Germany's Bild daily said.

The woman, identified as Jennifer, 29, a sales employee, is missing, and her husband Lars, a 30-year-old hospital nurse, is in a coma.

Jennifer's uncle told Bild: "We know that Lars is seriously injured and lying in a coma. Unfortunately we know nothing about the fate of my niece." So far, three fatalities have been named.

Adelma Marina Tapia Ruiz, a 37-year-old woman from Pucallpa in the Peruvian Amazon, was killed in the airport blasts, the foreign ministry in Lima confirmed.

She had been about to travel to New York with her Belgian journalist husband Christophe Delcambe and their three-year-old twin daughters.

The others survived the blast as the girls had run off and Delcambe had chased after them, though one of the girls was wounded by flying debris.

Another victim named was 20-year-old Belgian law student Leopold Hecht.

He was killed in the attack on a metro train close to the EU's institutional hub, said Pierre Jadoul, the rector of Brussels' Saint-Louis University.

"There are no words to describe our distress," he said.

Civil servant Olivier Delespesse was named among the dead by his employer, the Federation Wallonie-Bruxelles. He was killed in the metro attack, local media reported.

Some of those who had been listed as missing have subsequently been found in hospital.

Karen Northshield, a US personal trainer who had been at the airport, was in intensive care, according to friends.