The Turkish military has launched a series of counterattacks into northern Iraq after Kurdish rebels from the Kurdistan Workers' Party (PKK) killed 29 soldiers and police and five civilians along the border over the past two days.

Turkish combat planes and ground troops crossed the border into Kurdish-controlled northern Iraq Wednesday. Turkish news sources report that the attack has killed 21 PKK members.

Turkey's military response was launched only hours after a second attack by the PKK struck seven security posts in Hakkari province, near the Turkish border towns of Cukurca and Yuksekova. On Tuesday, PKK guerillas killed five policemen and four civilians in Bitlis province, also in the southeast.

The PKK is fighting for Kurdish independence in southeastern Turkey. The Kurdish homeland cuts across modern Turkey, Iraq, Iran, and parts of Syria. The rebel group is considered a terrorist organization by many states, including Turkey, the U.S., and the EU.

Immediately following the attacks, Turkish Prime Minister Recep Tayyip Erdogan called a crisis meeting, and announced an offensive against the PKK militants, which he said fell within the limits of international law.

The Turkish Republic, he declared in a televised news conference, will fight terrorists and their supporters to the end. Erdogan has suggested that other countries supported the Kurds in the attacks.

President Abdullah Gul also vowed swift retribution, warning great revenge for the attacks. Nobody should forget, Gul said, according to an ABC translation, that those who have inflicted this pain on us will suffer sharp, severe pain as a consequence.

The retalitory offensive is supported by the United States and NATO. The Turkish air force used bombers and helicopter gunships in the attack.

U.S. President Barack Obama condemned the PKK's outrageous terrorist attack, and promised to support Erdogan and Gul. [Turkey is] one of our closest and strongest allies, Obama said. He promised strong cooperation in the fight against the terrorist threat from the PKK, according to The Herald Sun.

The PKK assaults on Turkey reveal the political and security challenges that come from Iraq's fragile central government, as well as growing tensions within the country and in Turkey from extremist Kurds.

It is clearly unacceptable that Iraq's territory is being used to mount cross-border attacks against neighboring countries, said UN Secretary-General Ban Ki-Moon, according to AP Pakistan.

The United States has had a strong alliance with the Iraqi Kurds since 1991, when the U.S. shielded them with a no-fly zone outside Saddam Hussein's control following the first Persian Gulf War.

Since the U.S. invasion and overthrow of Saddam in 2003, however, the U.S. military has attempted to manage increasingly hostile conflicts between Kurds and Iraq's other ethnic groups, including attempts to control the PKK.

Despite reports that at least 20 rebels from the Kurdistan Workers' Party have been killed, PKK leader Duzdan Hammo insists that there were no rebel casualties, and that more Turks have died than have been reported by the press.

Turkish forces have provoked our fighters to conduct attacks, Hammo said in a phone interview with Kurdiu.

The government of the semi-autonomous Iraqi Kurdistan region called the PKK assault a crime that was against the interests of the Kurdish people.

Bayan Abdul Rahman, meanwhile, Kurdistan's representative in the UK, told The World Today that the Kurdistan Workers' Party had no relation to everyday Kurds in Iraq and in Turkey. When you hear the Turkish media, Rahman said, you would imagine that every street in Iraqi Kurdistan has at least one PKK base and they are part of everyday normal life, which is very, very far from the truth.

More than 40,000 people have been killed in Turkish-PKK conflict since 1984, when the Kurdistan Workers' Party first launched a violent and prolonged campaign for independence. In 2008, following a spike in PKK violence, Turkey crossed the border into Iraq.