At least four people were killed and 52 injured on Thursday when a bomb destroyed a military vehicle in a southeastern Turkish city, Prime Minister Tayyip Erdogan said.

The Anatolian state news agency later put the death toll at five and said it included two school students.

Diyarbakir is the biggest city of mainly Kurdish southeast Turkey and home to large numbers of troops who are battling PKK Kurdish rebels both inside Turkey and in nearby northern Iraq. The blast will keep up pressure on Turkey to strike PKK positions in northern Iraq.

"We will continue our fight against terrorism with the same determination, whether domestically or internationally," Erdogan told reporters. He said six people had been seriously injured.

Diyarbakir's governor said the total number of those hurt in the blast was 68. He said the bomb had been set off by remote control.

Turkish television showed vehicles engulfed in flames as ambulances and firefighters rushed to the scene. One man's face was covered with blood.

"The place where the explosion happened was full of people, there was a private school right in front of it," a police officer told Reuters.

A large hotel and shopping centre are near the site of the blast, as well as large military installations.

Several explosions happened one after another, witnesses said, but it was not clear whether the later blasts were caused by exploding fuel tanks or another bomb.

Turkish security forces have been on alert over the New Year for possible attacks by the Kurdistan Workers Party (PKK) and its supporters.

A woman was killed last week in a bomb blast in Istanbul, Turkey's largest city. An explosion in a garbage bin wounded three people on Wednesday in Istanbul.

Authorities suspect the PKK was behind both attacks, although no one has claimed responsibility.

NORTHERN IRAQ

Turkey's government and top generals have said the aerial bombing campaign of PKK positions in northern Iraq will continue "for as long as necessary".

Turkey, which has the second largest army in NATO, has massed up to 100,000 troops near the mountainous Iraqi border but has so far held back from a full-scale invasion. Commandos have conducted limited raids into Iraqi territory.

Ankara says it has the right to hit the PKK in Iraq under international law. The PKK has been using northern Iraq as a launchpad to stage attacks that have killed dozens of Turkish troops over the past few months.

Ankara blames the PKK for the deaths of nearly 40,000 people since the group launched its armed campaign for an ethnic homeland in southeast Turkey in 1984.

The United States and European Union, like Turkey, classify the PKK as a terrorist organisation. The U.S. military is sharing intelligence with Turkey to help combat the PKK though Washington has also urged Ankara to act with restraint.

U.S ambassador to Ankara, Ross Wilson, condemned the Diyarbakir bombing in a statement and pledged continued U.S. solidarity with Turkey in its fight against terrorism.

Military operations against the PKK are expected to top the agenda when Turkey's President Abdullah Gul meets U.S. President George W. Bush at the White House next Tuesday.