Bosnian show of unity masks hatred: The image of brave defenders fighting together against Serbian attacks is not what it seems, Robert Fisk writes from Mostar

THEY ARE there in their hundreds, under the pine trees in the lovers' park. Muslim crescents next to Christian crosses, scarcely six inches between each grave. Fresh graves, too. Every wooden headstone commemorates 1992 as the year of every young man's death. There are families under the pines, cleaning the wooden markers, adding flowers to the frosted earth, still in love with the dead. Strangers are unwelcome - as they are everywhere in Mostar - lest they uncover the secret of this little Sarajevo.

The parallel, of course, is an easy one. Although not surrounded, Mostar lies in the basin of the Neretva Valley, bombarded by Serbian guns positioned high above the snow-line to the east. Despite their suffering and the destruction of their magnificent old city, Mostar's Croat and Muslim defenders have refused to retreat. Another brave, embattled Bosnian population endures martyrdom. That, at least, is the story.

Nor should we doubt the pain involved. Drive out of Mostar towards Blagaj, where the mountains of Montenegro glower darkly on the horizon, and you can see with the naked eye a line of blackened armoured vehicles on the heights to the east, all that is left of a Croatian attack on the Serbian foothills last month. The Croats were annihilated, only a few of their wounded dragged back to the hospitals in Mostar.

Mostar itself has been wounded with equal cruelty. Almost every house of beauty in the Muslim sector of the city - on the eastern side of the Neretva, closer to the Serbs - has been destroyed by Serbian gunfire. Virtually every building in the old Turkish bazaar - the Kujundziluk - has been blitzed. A shell has torn through the minaret of the Karadjozbeg mosque, built by Mimar Sinan in 1557 - no one seems to know what has become of its 600-year-old Koran - and the roof of the Mehmet Pasha mosque has been partly torn away. Great hunks of masonry from the massive Turkish towers on each side of the 16th-century stone bridge - the first tower built in 1676, the second in 1716 - have been ripped off by artillery fire.

And then there is the bridge itself, symbol of Herzegovina, 'like a rainbow rising up to the Milky Way, leaping from sheer rock to sheer rock' above the Neretva, as a 17th-century traveller described it. Part of its northern parapet has been shot away, iron and wooden scaffolding now help to hold it together. Bullet holes scar the ancient stonework. Its architect used eggs and goats' hair as the only mortar between the stones but at least it is still there, propped up like a cripple.

But now come the questions. Why, for example, do the Croatian soldiers on the western side of the bridge stare with such hatred and suspicion at the Muslim militiamen less than 100 yards away on the eastern side? Allies against the Serbs they may be, but those bullets that hit the bridge were fired at each other by Croats and Muslims. And why is it that the older, Muslim quarter of Mostar has suffered so much more destruction from the Serbian guns than the Croatian side of the city? True, the Catholic church received a direct hit. But why are the two huge buildings housing the Croatian HVO army headquarters - the very nerve-centre of the defence of Mostar - untouched by Serbian shells?

Then there is the little question of supplies. Mostar's Croatian city fathers will tell you that, thanks to the United Nations, the population is supplied with food. The United Nations High Commissioner for Refugees delivers to both the Croatian humanitarian agency and the Muslim relief organisation. But neither will admit that, just a few days ago, Croatian HVO troops turned up at the Muslim warehouse and stole 80 per cent of the Muslim UNHCR food shipments at gunpoint.

And there are the refugees, hundreds of Muslim homeless now crowded into a freezing school gymnasium at Posusje, west of Mostar. There are no homes available to them, according to the Croatian authorities. So why are there up to 12,000 empty rooms in the Croatian village of Medjugorje, where Catholic pilgrims once flocked to worship where the Virgin is supposed to have appeared to a group of children in 1981? Why has the Christian church here not opened its heart to its Muslim brothers?

And there are the little red and blue maps, stuck on walls and noticeboards now as far west as Tomislavgrad, of a huge Croatia - within the frontiers of Croatia's Second World War Nazi puppet state - in which Bosnia-Herzegovina has entirely disappeared. For both Croats and Serbs, the Muslims of Bosnia-Herzegovina have no place in this plan.

Andrew Marr, page 19