A homemade bomb left on a bicycle exploded at a market in the Aegean port city of Izmir on Saturday, injuring 15 people, the governor said.

The blast occurred one day before hundreds of thousands of secular Turks were expected to march in the city against the Islamic-rooted government's attempts to raise the profile of Islam in the country.

Governor Cahit Kirac appealed for calm. Izmir's mayor, Aziz Kocaoglu, said he did not think there was any connection between the attack and the planned demonstration.

The blast occurred at a market in the Bornova district of Izmir in the morning as vendors were setting up their stalls. One of the injured had a serious wound in the ankle, authorities said.

The blast shattered the windows of several houses and car windshields.

Police were searching for a suspect who allegedly left the bicycle at the scene. Witnesses reported seeing a blue nylon bag on the bicycle, the state-run Anatolia news agency said.

There was no indication of who might be behind the attack. Kurdish, leftist and radical Islamic groups have carried out bombings in Turkey in the past.

Political tensions are high in the country after secular lawmakers blocked the election of a president from Prime Minister Recep Tayyip Erdogan's Islamic-rooted party, out of fear the nation's secularism would be undermined.

Erdogan's government declared early general elections in July. Parliament on Thursday amended the constitution to allow the Turkish people — rather than legislators — to elect the president. However, President Ahmet Necdet Sezer could veto the measure or call for a referendum on it.

Foreign Minister Abdullah Gul, whose bid for the presidency was blocked in the standoff over religion in politics, hinted Friday that he might revive his candidacy in any direct election by voters. Doing so would likely trigger further tensions over the presidency.

The powerful military, which has ousted four governments since 1960, has strongly warned the government against radical Islamic activities in the country and said it remains the "absolute defender" of the secular system.