EU voices mixed emotions about Yemen revolution

"Yemen is one of our principal concerns for our own national security ... it could become a much more serious threat to our own national security," he noted.

His remarks come after AQAP late last year put bombs on US-bound planes transiting through London and Dubai. But they stand in contrast to his enthusiastic endorsement of opposition forces in Libya following his visit to the rebel capital Benghazi over the weekend.

"It is quite inspiring ... to see their real hope for the future of their country," Hague said on Libya in the same TV interview.

European Parliament head Jerzy Buzek in a statement on Monday also emphasised the risk of post-Saleh instability: "All sides must urgently restore the ceasefire and stop fighting. This is first and foremost the responsibility of governmental authorities."

The head of the Liberal group in the EU parliament, Guy Verhofstadt, gave the only unequivocal endorsement of Saleh's apparent fall.

"May this be a warning for the dictators in Bahrain and Syria that killing its population instead of democratic reforms leads towards the end of the regime," he said.

Saleh on Sunday underwent surgery in neighbouring Saudi Arabia for shrapnel wounds and burns after a rocket hit his compound in Sanaa on Friday.

Opposition protesters over the weekend celebrated his downfall. But Saleh has promised to return after two weeks and sporadic fighting continued in both Sanaa and the southern city of Taiz in the early hours of Monday.

The president's deputy, Abd-Rabbou Mansour al-Hadi, has taken over for and has called a ceasefire with the Ahmar tribal group which reportedly led the assault on Saleh's base.

For its part, Saudi Arabia is expected to renew pressure on Saleh to sign a Gulf Co-operation Council agreement for him to step down in return for legal immunity for killings.

EU foreign relations chief Catherine Ashotn has stayed silent on Saleh's departure. But she urged all EU nationals to leave the country in a statement on Friday and said the European Commission will use its crisis management centre to help them get out.

In other Middle East developments, Syrian security forces killed 38 opposition supporters over the weekend and Israeli soldiers killed between 10 and 22 unarmed Palestinian protesters on the Israel-Syria border.

Meanwhile, Formula One authorities have decided to reschedule a race in Bahrain for later this year.

The original event was postponed due to killings of pro-democracy protesters in the capital Manama. Politicians and commentators have rounded on the decision, saying teams should boycott the grand prix in protest at government repression.

"Protestors were killed, tortured and imprisoned. These incidents need to be properly investigated and brought to justice - not swept under the carpet. Until this has happened, I fully agree that the Formula One grand prix should not return to Bahrain," the Liberal group's Verhofstadt said.

Correction: the original story said Israeli soldiers killed 22 Palestinian protesters. Latest reports at 3pm Brussels time on 6 June say Syria put the death toll at 23, while Israel gave lower figures