Police arrest a suspect in front of the US consulate in Casablanca on Saturday. (AFP)

Casablanca, April 14 (Reuters): Two suicide bombers blew themselves up outside US diplomatic offices in Morocco’s commercial hub Casablanca today in the first such attack in Morocco in four years, witnesses said.

Only the bombers were killed in the Casablanca attacks, no one was wounded.

Analysts say recent blasts in Morocco and the twin explosions that killed 33 in Algiers on Wednesday signal a sharp expansion in the threat from armed groups seeking to establish Islamic rule in north Africa.

The increasingly bold bombers are posing a tough test for governments trying to shore up stability in a region on Europe’s southern flank that is dependent to a large extent on oil and gas exports and tourism.

Today’s targeted suicide bombings in Casablanca were the first in Morocco since May 2003, when attackers set off at least five explosions in Casablanca that hit a Spanish restaurant, a five-star hotel and a Jewish community centre.

Forty-five people were killed, including 13 bombers, and about 60 were wounded in those attacks.

Witnesses said the first blast today happened about six metres from the US cultural centre and the second went off about 20 seconds later 60 metres away from the consulate.

Police arrested a third bomber as he tried to flee the scene in a smart district of the port city, where three suicide bombers blew themselves up four days ago. “He threw down his explosives belt and ran away. Police chased him and caught him,” said the owner of a coffee shop in the neighbourhood, who declined to be identified.

They also later arrested the leaders of the armed group to which the two suicide bombers and those responsible for Tuesday’s blasts belonged, a security official said.

The senior official, who spoke on condition of anonymity, said the two arrested men — the head and deputy head of the gang — had given investigators the names of the group’s members and their plans for future attacks.

A senior police source said Saturday's bombers clearly intended to attack the US buildings. “They made that statement with their own bodies,” the source said. He said the two could not get closer to the buildings due to security fortifications.