ISTANBUL — Kurdish rebels hijacked a ferry with 24 people aboard Friday in the sea of Marmara, where their leader Abdullah Ocalan is imprisoned on an island, Turkish Transport Minister Binali Yildirim said.

Four or five hijackers claiming to be Kurdish rebels seized the ferry off northwestern Turkey late Friday, he said in televised remarks.

"We think they are four or five ... They say they belong to a branch of the terrorist organisation," he added, referring to the banned Kurdistan Workers' Party (PKK).

More than five hours after the attack around 1700 GMT, the hostages were still on board the ferry off the coast of Selimpasa, west of Istanbul and about five nautical miles from the hijacking spot.

Television footage showed the blurry silhouette of the ferry from afar as coast guards did not allow the media to approach it.

The hijackers have conveyed demands for food and fuel through the captain, said the minister.

Asked if the demands would be fulfilled, Yildirim said, "We'll evaluate them." The private NTV television said five Turkish fuel tankers have been diverted to head toward Tekirdag on the Marmara sea's northern coast, where the ferry was being held.

The minister said 18 passengers, five of them women, four crew and two interns were aboard the ferry, the Kartepe, which was making its normal route along the northern coast of the Marmara sea.

One of the hijackers claimed to have a bomb and told the ferry's captain that he wanted media publicity, local mayor Ismail Karaosmanoglu told NTV.

Yildirim said the claims could not be verified.

Relatives of the ferry hostages were anxiously awaiting news in the ports of the cities of Izmir and Golcuk, the Anatolia news agency reported.

"We heard about it from the media. We couldn't establish any telephone connections, though we tried many times," a relative of one of the hostages told Anatolia.

The island of Imrali, where Ocalan, the jailed PKK leader, is being held, lies around 120 kilometres southwest of the hijacking spot. Turkish media say the hijackers may be heading for the island.

Pro-Kurdish demonstrations are regularly held in Turkish cities in support of Ocalan, who is still considered the PKK's chief despite his imprisonment.

Yildirim said the hijacked Kartepe was being shadowed by coast guard ships, adding they had not had direct contact with the rebels but had managed brief exchanges with the captain.

The PKK, listed as a terrorist organisation by Turkey and much of the international community, took up arms for Kurdish independence in southeastern Turkey in 1984, sparking a conflict that has claimed some 45,000 lives.

Clashes between the PKK and the army have escalated since mid-2011.

A surge of attacks by PKK rebels also caused civilian deaths in Turkey, prompting the Turkish military to launch in October a cross-border operation against rebel hideouts in northern Iraq.

The army operations were mostly concentrated in Turkey's southeast as well as a few areas in the north of Iraq.

Observers say the military action was in response to a domestic outcry but offered no solution to the root of the problem.

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