Photos & Pictures 20 Tourists and Other Killed at Prominent Tunisian Museum

One of the two gunmen who killed 20 tourists and others at a prominent Tunisian museum was known to intelligence services, Tunisia's prime minister said Thursday, but no formal links to a particular terrorist group have been established.

Police launched an intensive manhunt following the attack for accomplices, and a statement from the president's office said nine people linked to the gunmen had been detained Thursday, according to the French news agency AFP.

"The security forces were able to arrest four people directly linked to the (terrorist) operation and five suspected of having ties to the cell," AFP quoted the statement as saying.

The dramatic attack at the National Bardo Museum on Wednesday was the worst in years in Tunisia and a blow to its young and fragile democracy. It also threatened new troubles for the tourism industry, which brings throngs of foreigners every year to its Mediterranean beaches, desert oases and Roman ruins and had just started to recover after years of slump.

The death toll rose by two Thursday morning, as the Health Ministry said 20 tourists were killed rather than the 17 confirmed Wednesday. Three Tunisian nationals also were killed. But there as also some good news, as CBS News correspondent Allen Pizzey reported, two Spanish tourists were found still hiding inside an office at the museum Thursday morning, apparently unharmed. They were taken to hospital for medical checks.