Four Killed in Turkish Blasts Ahead of Summit

The attack on a public bus in Istanbul occurred only hours after a small bomb exploded outside a hotel in the capital Ankara where Bush is expected to stay on Saturday.

Four people including the bomber were killed and at least seventeen others injured in the Istanbul blast, which occurred outside a hospital in the European district of the city despite a massive security operation.

Police have detained three suspects in connection with the bus explosion -- two men and a woman -- who are believed to have been on the bus at the time of the blast.

The bombing came seven months after a wave of deadly attacks against British and Jewish targets in Istanbul. Those blasts were carried out by four suicide bombers, suspected members of a local al Qaeda-linked cell, who detonated explosive-laden trucks, claiming 63 lives and leaving hundreds of people injured.

U.S. diplomatic sources had said before the Istanbul blast that there were no immediate plans to change Bush's schedule, although the Turkish authorities pledged to boost security after the Ankara attack.

Istanbul is to host the NATO summit on June 28 and 29.

The U.S. leader is due to arrive in Ankara on Saturday for talks with Turkish officials on Sunday and will then travel on to Istanbul for the two-day NATO meeting.

A "percussion bomb"

Two of the wounded in the Ankara blast were policemen who were inspecting a suspicious parcel when it blew up near the entrance to the Hilton hotel, police chief Ercument Yilmaz said.

One of the officers was seriously injured in both feet and risked amputation, while the other policeman and the civilian suffered minor injuries, hospital sources said. Yilmaz told Anatolia news agency the blast was caused by a "percussion bomb" -- a device which is designed mainly to cause loud noise rather than damage and which is frequently used by underground groups in Turkey.

"I thought lightning had struck ... I ran 100 yards to the spot and saw a policeman lying in a pool of blood," said Mithat Aksoy, a cab driver who was waiting for customers at a nearby taxi station when the blast occurred.

"His foot was blown away and another officer was standing next to him in a state of shock," he added. The blast also damaged a nearby car and broke windows of neighboring buildings.

In other quarters of Ankara, police examined a suspicious parcel outside the foreign ministry and defused another outside the education ministry, Anatolia reported. Both packages turned out to be harmless.

Security to be beefed up

Deputy Prime Minister Mehmet Ali Sahin said security measures would be stepped up further. "Measures will be tightened even more. There are people who will stop at nothing to accomplish their evil intentions. It is up to us to use all measures against them," Sahin said, according to Anatolia.

A U.S. embassy official had said before the Istanbul blast that there were no immediate plans of changes to Bush's schedule. "Security has been a high priority and it will continue to be so. All measures needed will be taken," he added.

Apart from Islamist extremists, far-left and Kurdish separatist groups are active in Turkey. They have frequently carried out similar attacks in the past.

A radical Marxist group has claimed responsibility for the Ankara explosion, Reuters news agency reported, citing NTV television. NTV identified the group as the Marxist-Leninist Communist Party, a small Turkish group which has carried out minor attacks on official targets over the years.

Authorities in the Turkish capital were already on high alert

ahead of Bush's arrival, which will be preceded by a mass

demonstration against U.S. policies in Iraq and the Middle East.

"All leave has been cancelled in the police department. At least 10,000 officers will be on duty," a police official told AFP.

Massive security measures are also in place for the June 28-29 NATO summit in Istanbul, a sprawling metropolis which has long been a playground for underground groups.

In recent weeks, there have been a number of small bomb attacks in Istanbul and other Turkish cities, similar to those carried out in the past by anti-US and anti-NATO left-wing militants.

In the run-up to the NATO summit, Turkish security forces have detained dozens in security sweeps across the country against several outlawed groups.