LONDON — Four top suspects in the attempted attacks on the London transport system July 21, including a previously unidentified man linked to a knapsack bomb found in a park, pleaded not guilty yesterday in an appearance at a high-security court.

As police helicopters circled above, the top-security courtroom at Belmarsh Prison also became the stage for the first appearance by three suspects, all East African refugees or immigrants, whose faces became internationally known during a manhunt last month. Police say security cameras filmed the three, whose knapsack bombs failed to fully detonate.

A fourth suspect caught on video remains in custody in Rome, where he had fled by train and was found hiding at his brother's apartment.

Muktar Said Ibrahim, 27, an Eritrea-born Briton who frequented a radical London mosque, has been identified as the ringleader in a confession by the suspect held in Rome, Italian investigators say.

Ibrahim pleaded not guilty yesterday to charges of attempted murder, conspiracy to murder and using explosives in connection with the attempted attack on a double-decker bus.

The same charges have been filed against Ramzi Mohammed, 23, captured with Ibrahim in a raid on a housing project in Notting Hill July 31, and Yassin Hassan Omar, arrested in Birmingham two days earlier. Mohammed and Omar denied trying to bomb subway trains. Like Ibrahim, they remained impassive in court.

The hearing also featured appearances by Mohammed's brother, Wharbi, and two Ethiopian-born men. All three are accused of helping the fugitives.

Yesterday's hearing also gave a first glimpse at Manfo Kwaku Asiedu, who was arrested July 26 in a North London neighborhood close to where Mohammed and Hassan lived. He allegedly has been linked to a knapsack bomb that was found abandoned in a park in West London two days after the failed attacks.

The find led to the theory that the original plot included a fifth bomber who never reached his intended target. Prosecutors did not specify yesterday why the fifth bomb was not used or explain Asiedu's alleged role.

Asiedu, 32, pleaded not guilty to charges of conspiring to murder passengers using explosives.

Asiedu was accompanied by an interpreter of the Twi language of Ghana. Police did not disclose his birthplace, but said he has lived in the Finsbury Park area. The suspects worshipped at a radical mosque in that north London neighborhood, Italian investigators say.

In keeping with rules about disclosing evidence, prosecutors provided few details.

Other developments

• French intelligence produced a report shortly before the London suicide bombings saying al-Qaida planned to attack Britain and would use Britain's large Pakistani community to strike, Le Figaro newspaper reported yesterday.

Written in late June, the 20-page report on the Pakistani community in France said: "The United Kingdom remains threatened by plans decided at the highest level of al-Qaida. ... They will be carried out by agents who will take advantage of the pro-jihad sympathies within the large Pakistani community in the United Kingdom." Three of the four bombers who carried out the July 7 attacks were Britons of Pakistani origin.

• A fundamentalist Muslim cleric facing possible treason charges in Britain has left the country, British media reported yesterday.

Sheik Omar Bakri, founder and spiritual leader of the radical Islamic group al-Muhajiroun, has been identified by British officials as one of a number of radical clerics who could face charges if their public remarks are deemed to have incited terrorism.

The report, which also was carried by Sky News and British Broadcasting Corp., could not immediately be confirmed.

Al-Muhajiroun is to be banned under anti-terror laws unveiled by Prime Minister Tony Blair last week. Bakri, 46, a Syrian native who came to Britain in 1985 after he was deported from Saudi Arabia, has claimed the group stopped its activities in Britain.

But in remarks following the July 7 London bombings, Bakri reportedly said that he would not inform police if he knew Muslims were planning another attack. He also reportedly offered support for insurgents who attack troops in Iraq and Afghanistan.

Information from Reuters

and The Associated Press

is included in this report.