As bells tolled from nearby churches, some 200 journalists and politicians stood for one hour in silence Friday to mourn a colleague who was killed in a car bomb the day before.

The crowd in downtown Martyrs' Square (search) held photos of Samir Kassir (search), the prominent anti-Syrian journalist slain Thursday, and raised black pens to symbolize freedom of expression. At the end of the hour, they sang the national anthem.

Kassir was killed inside his car at midmorning in the Christian Beirut neighborhood of Ashrafieh, where he lived. The bomb set the car afire and shattered windows in nearby buildings.

The opposition accused Syria of interfering in Lebanon's politics and called for a general strike on Friday. An-Nahar newspaper, for which Kassir was a columnist, staged the silent protest just 200 yards from its office building.

Many schools closed, while others suspended classes. But the call for a widespread strike came too late for many people to heed. Only a handful of shops were closed in Ashrafieh.

Kassir, 45 and a Christian, was a university professor and founding member of the Democratic Left Movement, a small group that joined the anti-Syrian opposition and played an active role in the protest campaign against Damascus' control. He wrote a column in An-Nahar, a leading newspaper that frequently criticizes Syria, and was a regular on TV talk shows.

In a recent television appearance, he said he had long received threats by security agents trying to silence him.

Interior Minister Hassan Sabei said initial reports indicated the bomb that killed Kassir was placed under the car and detonated by remote control.

Prime Minister Najib Mikati vowed that his government "will not allow anyone to target security and freedom."

Giselle Khoury, Kassir's wife, demanded an international investigation into her husband's death, Al-Arabiya satellite channel reported. Khoury, a journalist who works for Al-Arabiya, was in the United States at the time of the explosion.

Kassir will be buried in Beirut Saturday.

The bombing came as an international team was investigating the February assassination of former Premier Rafik Hariri (search), whose death led to the ouster of Syrian troops after nearly three decades in Lebanon. It also happened days before Sunday's second round of parliamentary elections — a ballot the anti-Syrian opposition hopes to win and end Damascus' control of the legislature.

Anti-Syrian leaders were quick to make a link between the two killings. Hariri's son and political heir, Saad Hariri, said the same people were behind both assassinations, "and God knows what's coming."

"We will not be afraid. ... We want our freedom, we want our independence, we want our sovereignty and no one is going to stop us," a defiant Hariri told reporters.

Syria strongly denied it was behind Kassir's killing and stressed its determination not to interfere in internal Lebanese affairs.

Opposition politicians and the United States claim Syria has kept intelligence agents in Lebanon, a charge Damascus also denies. Lebanon's opposition blames the Syrian-Lebanese intelligence apparatus for a series of bombings of commercial areas in recent months that have killed three people and wounded more than two dozen.

In a meeting Thursday night, the opposition reiterated calls for the resignation of President Emile Lahoud (search), a Syrian ally.

"Samir Kassir was assassinated by the remnants of the security agencies that control the country and that is headed by Emile Lahoud," Walid Jumblatt, a vocal opponent of Syria, said on Future television.

Lahoud condemned the bombing. "Today, the vicious hand is striking us in Lebanon," he told reporters.

In Washington, Secretary of State Condoleezza Rice condemned the attack as a "heinous act." Visiting European Union foreign policy chief Javier Solana said it was a tragedy, adding that Kassir was "a very honest man." U.S. Ambassador to Beirut Jeffrey D. Feltman said Kassir had symbolized Lebanon's "desire for freedom, sovereignty and democracy."