Riad Taha, the respected president of the Lebanese Publishers' Association, was machinegunned to death with his chauffeur here today after a futile breakneck effort to elude the unknown assailants.

The daylight assassination of the 53-year-old publisher was the second killing of an important Lebanese journalist this year, and highlighted a series and gun attacks and telephone threats aimed at both local and foreign journalists in this civil-war scarred capital.

Taha's death further undercut negotiations among Lebanon's divided political leaders to form a government of national unity to replace that of caretaker Premier Selim Hoss, who resigned last month.

President Elias Sarkis has asked Takieddin Solh, 71, one of the fathers of Lebanon's fragile independence, to try to form a new government. So far his efforts have failed.

According to security police, Taha, president of the publishers' association for the past 13 years, was attacked by four unknown gunmen as he drove through the Raouche section of West Beirut on his way to pay respects to outgoing Premier Hoss. Taha's drive made a desperate try to outrace the gunmen, who concerned the car and riddled it in front of the Hotel Continental.

The assassination was denounced as an effort to intimidate the Lebanese press, long the freest in the Arab world. Hoss termed the killing "a cowardly act against liberty." Premier-designate Sohl said it was "a crime against Lebanon, liberty and the printed word."

The Labanese Press Association declared a two-day protest strike and a two-week mourning period. Beirut Radio switched to classical music programs for the day as a sign of mourning.

Taha's death reinforced fears in Beirut of a conspiracy to frighten journalists into silence and recalled the case of Salim Lawzi, the editor of al Hawadess, a weekly he had moved to London during the Lebanese civil war four years ago.

Lawzi was kidnapped near Beirut international airport in February after he ignored threats and returned to Lebanon for his mother's funeral. He was found dead two weeks later in a woods south of the capital. He had been tortured and his writing hand had been mutilated.

Since then, a Syrian Freelancer, Issam Jundi, has been killed in equally mysterious circumstances and last month Bernd Debussman, the Reuter news agency bureau chief in Beirut, narrowly escaped death after he was shot in the back on leaving a journalists birthday party.

Two BBC correspondents also received death threats recently and have left Beirut. Yesterday, Charles Rizk, head of Lebanese television, resigned after having been kidnaped and held for four hours by gunmen.

"With Taha, press freedom and democracy were executed in Lebanon," the Lebanese Press Association lamented in a communique. "The silencing of the Lebanese press is tantamount to strangling the press throughout the Arab world."