The 43,000-tonne Volganest 248 ran aground just meters from the coast of the up-market city suburb of Kucukcekmece at around 6am yesterday. Its cargo of fuel oil began spilling into the waters at the entrance to the Bosporus, the narrow channel that runs through the heart of Istanbul.
With helicopters flying overhead and coastguard vessels tied alongside, the ship made a forlorn picture when daylight broke. The bow section had been torn off by winds of 35 to 40 knots (70mph) as the ageing vessel battled to head away from Istanbul into the Sea of Marmara.
"The front section broke off and sank," said coastguard chief Orhan Karaahmetoglu. "Which means its two forward oil tanks went down too. One of these has broken up already and is emptying itself straight into the sea."
Along the coast, still battered by high waves and gusting winds, a black slick has washed ashore. At the Florya tea gardens, a shoreline favourite in summer for residents, the terraces are blackened with oil, while huge clots of fuel continue to wash up with the grey breakers.
When the vessel broke in two, five of the 17 crew were trapped on the slowly submerging forward half. Coastguards battled with the elements to get them off, and all were rescued. Coastal safety and salvage workers were last night attempting to pump out the other tanks in order to prevent further spills.
"For years we've been saying that the Bosporus is not a safe place for these boats," said Gul Keydar, a local resident. "This is not a pipeline. Now our shore is ruined."
The narrow Bosporus has recently been the battleground for environmentalists determined to prevent tankers from carrying potentially harmful oil and chemicals through it. They argue that a collision could be fatal for many of Istanbul's 10 million inhabitants, who are crowded around the channel's shores.
Two tankers and one container ship have already run aground in the Bosporus this month, and plans to transport newly discovered Central Asian oil through the channel to Western markets have been strongly resisted.
Yet the straits are international waters, giving Turkey little legal clout in trying to impose safety standards on ships using them. In one transit of the Bosporus, vessels must make at least 12 course changes and battle strong currents and whirlpools. As a result, old and underpowered vessels, often from the former Soviet countries, sometimes have difficulty in maintaining steerage, leading to loss of control, collisions and groundings.
"There are vortexes and cross currents in the straits," explained Professor Najat Ince of Istanbul Technical University Foundation, who spent years developing a projected safety system for the channels. "These vary with the seasons and the winds and are very dangerous. A ship hits these and the captain slows down to try to handle them, but then loses control."
Yet taking a pilot on board is still optional, as is using the local ship traffic control. In winter, the city is battered by a strong south- westerly wind, the Lodos, which, in the early hours of Wednesday, pushed the Volganest 248 off course on to the shallows off Kucukcekmece, and sank 15 smaller boats at anchor in a marina on the Asian side of Istanbul.
"I think this time they were also sailing with their tanks half full,"Mr Karaahmetoglu said. "So in the strong winds, they get rocked from side to side and the fuel oil also moved around, unbalancing the ship."
Some 500 tonnes of oil have already flooded out, and the danger is that in the strong winds the ship may break up further, releasing more of its cargo. The local currents will then take this back up towards the city itself.
"We have to move fast," said Mr Karaahmetoglu, on the shoreline at Kucukcekmece, the floundered tanker rocking slightly in the charging water some 50 meters out. "We can't afford for this to get any worse."