The two Vietnamese men, aged 29 and 31, were arrested on Monday after the shootings took place in the small hours of Monday in the popular Lin Yue Chinese restaurant in Sittensen, situated between Bremen and Hamburg.

"My client told me he has nothing to do with this, and neither does his friend," said Wilfried Behrendt, who is representing the 31-year-old suspect.

He said he had applied for the release of his client and expressed his belief that a fellow lawyer for the other suspect would follow suit.

The two Vietnamese, whose identities have not been made public, are kept in custody by a magistrate in the town of Wildeshausen. They were arrested when their rental car was stopped for a "routine check" near the northern city of Bremen.

Media reports said that the 31-year-old had previously been investigated for criminal assault and blackmail, but police declined to comment on this, according to German media.

Behrendt admitted that he had represented his client for several years, but declined to elaborate.

Three apartments belonging to the Vietnamese men in Bremen and nearby Ahlhorn have been searched, police said, adding some documents had been seized but declined to give further details.

Six people, three women and three men, were found tied up and shot dead in the small hours of Monday in the Lin Yue restaurant in Sittensen. A seventh victim perished later Monday of his injuries.

One of the victims' husband alerted police at 12:30 local time (1130 GMT) when he went to retrieve his wife from work in the Lin Yue restaurant.

Police said that they still had no idea about the motive for the killings.

Four of the seven victims have been identified on Wednesday.

The owners of the restaurant, a Hong Kong Chinese couple with British passports, respectively aged 36 and 28, are among the dead.

Their daughter, 2, was found unharmed at the restaurant and was in good health, police said.

A 36-year-old woman waitress of Malaysian and a Thai man, 31, were among the identified.

The process of identifying the other three dead was completed Thursday but yet to be announced, media reports said.

A Chinese diplomat based in Hamburg told Xinhua on Tuesday that none of the victims were holding Chinese passports.

A murder inquiry was launched and local police have asked federal specialists to join the investigation.