ANKARA, JAN. 30 -- Gunmen shot and killed a prominent retired Turkish army general today, in what appeared to be the most violent of a series of attacks here since President Turgut Ozal's decision to allow U.S. warplanes to use Turkish bases to attack Iraq.

Lt. Gen. Hulusi Sayin -- senior security adviser to Premier Yildirim Akbulut and former security chief of southeastern Turkey, where Marxist Kurds have been fighting for political autonomy -- was shot four times in the head as he and his wife drove up to their home here just after dark.

Turkish media said three gunmen left a note at the scene saying that a leftist revolutionary group called Dev Sol had killed the 64-year-old officer on grounds that he "was a tool of imperialism."

Later, however, national police commander Necettin Belcin told reporters that other evidence suggested a radical Kurdish group may have carried out the killing in retaliation for hundreds of casualties inflicted by Turkish forces on Kurdish rebels in their ancestral homeland near the Syrian and Iraqi borders.

Since the Persian Gulf War began two weeks ago, Dev Sol, an urban guerrilla group that flourished during the political instability of the 1970s here, has claimed responsibility for a string of bombings against U.S. and other Western targets in Istanbul, Izmir, Adana and Ankara. But these attacks have caused relatively minor property damage and slight injuries to a few bystanders.

In the latest incidents, bombs exploded in Istanbul late Tuesday outside an American Catholic immigration-aid office, a British insurance company and the Italian consulate, causing little damage.

Today, only hours before the slaying of Sayin, one Western diplomat belittled the current Dev Sol campaign as a "wavelet of bombings carried out by domestic leftists who just want to show they're still around," and he questioned whether the group -- responsible for many of the estimated 5,000 political killings here in the 1970s that led to an army coup in 1980 -- was "still a coherent organization."

Another Western diplomat described most of the recent bombings as "joke stuff using a pound of black powder and a wick," rather than the sophisticated plastic explosives used by more technically adept Middle Eastern terror groups.

Neither diplomat suggested that the current violence in Turkey was directly inspired by Iraq as part of its repeated threats to strike at targets connected with the U.S.-led coalition fighting to force Iraqi troops to withdraw from occupied Kuwait.

In neighboring Greece, however, a guerrilla band called the November 17 Group claimed in a letter to an Athens newspaper today that it had staged all six bomb and rocket-propelled-grenade attacks reported in the city in the past two weeks to fight "the barbarous Western assault" on Iraq. Police said the letter was genuine.

The attacks have seriously damaged U.S., British and French properties -- including the offices of American Express and British Petroleum -- and Greek Public Order Minister Yannis Vassiliadis declared today that "Greek terrorism has joined with {Iraqi leader} Saddam Hussein in bringing the gulf war to our country."

Attacks by the Marxist-oriented guerrillas have forced the Greek government to adopt the strictest security measures seen in Athens since the 1967-74 military dictatorship, as more than 1,000 police reinforcements were called in to help guard possible terrorist targets.

In Lebanon, meanwhile, a 12th bomb blast since the start of the gulf war was reported outside the long-vacant Beirut embassy of the Persian Gulf emirate of Qatar, a member of the anti-Iraq military coalition. No damage or injuries were reported. Previous bombings in Lebanon targeted the Italian Embassy, British, French and Saudi banks and a Bekaa Valley branch of the American University of Beirut. At least one person, a bank guard, has been killed.

{In a related development, the Reuter news agency reported from Bangkok that Thai authorities had asked six Iraqi diplomats to leave the country and that police had taken into custody four Arabs suspected of being pro-Iraqi terrorists and were searching for others.}

Recent news reports from Bangkok have indicated concern there that pro-Iraqi guerrillas might seek to use the country as a staging center for terror attacks throughout the region, including the Philippines.