Turkey's domestic political crisis deepens as bombings up the pressure all round, writes Gareth Jenkins Late Sunday evening, two bombs exploded in a busy pedestrian-only street in the working class neighbourhood of Gungoren in the heart of Istanbul. A total of 17 people were killed and over 150 injured. Unlike other recent attacks in Turkey, the explosions in Gungoren appear to have been designed solely to kill civilians. There were no obvious targets -- such as buildings associated with the Turkish authorities or foreign interests -- in Menderes Street, where the bombings took place. The first, relatively small, bomb exploded in a garbage can around 9.45pm local time. Ten minutes later, as the area thronged with people trying to help those injured in the first blast, a second, much larger bomb exploded. Five of the dead were children; including two cousins aged three and four years old taken by their families for ice cream. The use of two successive explosions to maximise casualties -- one to gather and concentrate the intended victims, the second to kill them -- is familiar from other countries, particularly from the carnage that has followed the US occupation of Iraq. But it is the first time that it has been used in Turkey. Traditionally, although militant groups in Turkey have often been prepared to inflict civilian casualties, it has been part of an attack on an economic or symbolic political target, such as government institutions and officials, foreign interests, religious minorities, infrastructure or the tourism industry. The bombings in Gungoren were the first that sought only to kill as many ordinary people as possible. It is still unclear who was responsible for the attack. The absence of any symbolic target would appear to rule out ideologically driven groups such as violent Islamists or leftists. On Monday, Turkish Prime Minister implicitly blamed the separatist Kurdistan Workers' Party (PKK) by describing the bombings as part of "the cost" of Turkey's air strikes against the organisation's camps and bases and northern Iraq. A few hours before the explosions in Gungoren, Turkish warplanes bombed 12 PKK targets in northern Iraq in the latest in a series of cross-border air strikes that started in December 2007. In recent months there has been speculation that, forced onto the defensive in northern Iraq and apparently unable to make any headway in its rural insurgency in southeast Turkey, the PKK might attempt a show of force by staging a large- scale bomb attack in the west of the country. But, like other militant groups, the PKK has no previous record of staging attacks with the sole purpose of killing as many Turkish citizens as possible. If the PKK was responsible for the bombings in Gungoren, they not only represent a new phase in its campaign of violence but also will further strain the organisation's relations with Iraqi Kurds. In recent years, a sense of ethnic solidarity has meant that Iraqi Kurds have been prepared to tolerate the presence of the PKK in the mountains of northern Iraq, provided that its insurgency uses only traditional guerrilla tactics and does not provide Turkey with a pretext to interfere in internal developments inside Iraq. Many Iraqi Kurds believe that Ankara will use the PKK as an excuse to intervene in northern Iraq to prevent Iraqi Kurds from realising their long-term dream of establishing an independent political entity in the north of the country. Even before last Sunday's bombings, Iraqi Kurdish officials privately expressed their frustration at what appears to be a new, more reckless, policy pursued by the PKK as exemplified by the organisation's kidnapping last month of three German mountaineers in eastern Turkey. In addition to antagonising Ankara, such actions also increase international pressure on Iraqi Kurds -- particularly from the EU -- to move against PKK camps in northern Iraq; something which, given the nature of the mountainous terrain, would be very difficult militarily and, given the widespread sympathy for the PKK amongst the Iraqi Kurdish population, very risky politically. The bombings in Gungoren also came at a time of renewed tensions between Turkey and Iraqi Kurds over the future of oil-rich Kirkuk. The province currently lies outside the territory officially administered by the semi-autonomous Kurdistan Regional Government (KRG) in northern Iraq, which has long pressed for a referendum on its future status. Few doubt that if the referendum is ever held the large Kurdish population in Kirkuk will ensure that the province is transferred to the authority of the KRG. Turkey fears that the oilfields of Kirkuk could be used as the economic foundations of an independent Kurdish state and has warned that it will oppose the holding of a referendum. The KRG has recently begun to push for the referendum to be held in November this year. In July, Turkish Foreign Minister Ali Babacan repeated Turkey's determination to prevent the referendum ever taking place. "There has been no change in our position," warned Babacan. Meanwhile, there are doubts about whether Babacan will still be in his post in autumn this year. On Monday, Turkey's Constitutional Court began its final discussions in a case filed in March 2008 for the closure of the ruling Justice and Development Party (JDP) on the grounds that it has become a focus for anti-secular activities. Most analysts predict that the court will eventually decide to close the JDP and ban Erdogan from membership of a political party for a period of five years. If the JDP is closed, Turkey is expected to head for an early election in November or December this year. Any election campaign is likely to be fought on two issues, secularism and nationalism, making it very difficult for any government in Ankara not to deliver on Turkey's threats to prevent the Kirkuk referendum from being held.