Central Rome came to a standstill Monday as Italy bade a solemn farewell to an intelligence officer slain by US gunfire as he escorted a freed Italian hostage to safety in Iraq.

Mourners applauded as the coffin carrying the body of Nicola Calipari was borne into the Santa Maria degli Angeli (Saint Mary of the Angels) basilica by officers from combined Italian military services after a bugler played the Last Post.

Calipari, lauded as a hero for saving journalist Giuliana Sgrena's life as he shielded her with his body from US gunfire on a convoy that was taking her to safety near Baghdad, was given a full state funeral.

In an address to the congregation, Italy's minister with responsibility for the intelligence service, Gianni Letta, called for the diplomatic and political row over his killing to be momentarily set aside.

"This is a time to pay homage together, without arguments, to the heroic gesture of Nicola Calipari," said Letta in an oblique reference to Rome's diplomatic spat with Washington, and fears over a rising chorus of anti-Americanism on the Italian left, which fiercely opposed the US-led war on Iraq and the subsequent deployment of Italian troops.

Letta paid tribute to Calipari's "reserve and discretion" in Iraq while carrying out his duties as Italy's top intelligence officer.

President Carlo Azeglio Ciampi headed a high-profile cast of political and military figures, including Prime Minister Silvio Berlusconi. Behind him sat US Ambassador Mel Sembler, who was called in by the prime minister as Italy formally protested the "friendly fire" incident on Friday.

Ciampi, 84, for many Italians the father of the nation, comforted Calipari's distraught widow Rosa Maria and her teenaged children during the ceremony.

More than a thousand people packed into the basilica, on the city's Republic Square. Millions more watched the moving ceremony live on television.

At the end of the two-hour service, thousands of people packing the square outside the church gave loud and steady applause as the coffin, wrapped in the Italian tricolour, was borne through an honour guard and placed in a waiting hearse. Calipari was buried in the nearby Verano cemetery.

Earlier, traffic in the city centre came to a standstill and passers-by stood to attention, made the sign of the cross and clapped as the funeral procession rolled past on its two-kilometre (one mile) journey to the basilica from the city's Vittoriano war memorial.

Organisers estimated 100,000 people had lined up to pay their respects as Calipari's body lay in state at the monument from early on Sunday through the night.

"I'm here because Nicola Calipari performed a great service for peace with the professionalism which already pushed him to save the two Simonas," said 70-year-old Giusto Previsiol, who clapped as the cortege passed along the city's Via Nazionale.

Calipari had previously been involved in negotiating the release of two Italian aid workers, Simona Pari and Simona Torretta, held hostage last year for nearly two months.

"It's not every day that one comes across a hero. He did his duty, and made the ultimate sacrifice to save her," said businessman Valeriano Farcas, 32, visibly moved as the cortege passed by.

Ciampi is to posthumously award him Italy's highest honour for bravery.

Monday's scenes of grieving were reminiscent of the state funeral for 19 Italians killed in a truck bombing of their heaquarters in Nasiriyah two years ago.

But this time the anger runs deeper, and is unlikely to be placated by Washington's promises of a full investigation into the incident.

"All Italy demands that the United States give an account of what happened," said Deputy Prime Minister Marco Follini.

"It demands, and I underline the word, clear answers and will not content itself with vague responses," Follini said in an interview published Monday in Rome's conservative Il Messaggero daily.

The White House on Monday rejected as "absurd" Sgrena's repeated suggestion in media interviews that she had been deliberately targeted by US troops, because Washington strongly opposed the kind of negotiations Calipari conducted to free her.

"It's absurd to make any such suggestion, that our men and women in uniform would deliberately target innocent civilians. That's just absurd," spokesman Scott McClellan told reporters.

Italy will not allow the matter to rest, however.

"Today we paid homage to a valiant man, tomorrow we will renew our demand for justice," said former left-wing prime minister Massimo D'Alema, president of the largest opposition party.

Meanwhile Bulgaria, which has 450 troops deployed in Iraq, on Monday also demanded a US explanation for a "friendly fire" incident which left a Bulgarian soldier dead last week on a road some 100 miles (160 kilometers) from Baghdad.