Yemeni security forces arrested six alleged al Qaeda militants on Tuesday for plotting attacks on foreign and local targets, the new unity government said.

The announcement came a day after a jail break in which security sources told Reuters seven al Qaeda prisoners had escaped, highlighting Yemen's patchy record against the militant group.

They were among 16 who tunnelled their way out of a prison in Aden, although an interior ministry official denied any al Qaeda link.

The United States and neighbouring Saudi Arabia fear the network is exploiting political upheaval that has weakened central government control over swathes of Yemen.

The government, formed after outgoing President Ali Abdullah Saleh signed a deal last month to hand over power after months of protests, is simultaneously facing an emboldened separatist movement in the south and Shi'ite Muslim rebels in the north.

The state news agency Saba carried mug shots of the alleged al Qaeda members, included the suspected leader of a cell that attacked Sanaa airport in 2009.

These elements were conducting surveillance (on) targets they wanted to conduct terrorist operations against, including leaders and prominent state figures as well as government facilities and Arab and foreign missions, Saba quoted a security source as saying.

Those arrested are also accused of recruiting youths to fight along with militants in other Yemeni provinces.

DIPLOMATIC BOOST

Ambassadors of the five U.N. Security Council members and Gulf Arab diplomats on Tuesday met government officials and a committee overseeing a ceasefire in Yemen's commercial capital Taiz, where fighting had raged in recent weeks.

They said they would support the national unity government's efforts to tackle the impact of the clashes in Taiz, said Abdullah Noman, an opposition leader who attended the meeting. The ambassadors focused on the future, on reconstruction efforts.

Saleh loyalists and opponents began withdrawing from the streets of Taiz last week after a fragile truce was agreed to put an end to street battles in which dozens were killed.

Under a plan brokered by Gulf Arab states with the help of a U.N. envoy, members of Saleh's General People's Congress (GPC) and opposition parties divided cabinet posts between them to form a cabinet that will lead the country to presidential elections next February.

The U.N. envoy who helped clinch the power transfer deal visited the northern province of Saada on Tuesday in a bid to talk northern rebels known as Houthis into cooperating with the new government, which was sworn in on Saturday.

In the case of Yemen there are many stakeholders and if one or two stakeholders have the perception that they are excluded they will become spoilers of the process, said Jamal Benomar after meeting the self-proclaimed governor of the province and Houthi representatives.

His visit to Saada, the first by an international official since 2004, came as fighting continued between the Shi'ite Houthi rebels and Sunni Salafi fighters. Both sides reported dozens of deaths in clashes this week.

What is needed is for the Houthis to participate as a political party, a political force and not as a militia or an insurgency, said Benomar.

DETAINEES FREED

Yemen's interior minister on Tuesday ordered the release of all detainees held in connection with nearly 11 months of protests in Sanaa, the state news agency said, although activist Mane' al-Mutairi told Reuters it was not clear if all had been freed.

Helene Kadi, emergency coordinator in Yemen for the United Nations Children's Fund (UNICEF) told a news briefing in Geneva the humanitarian situation would remain very dire despite the political deal for Saleh to step down.

The agency has appealed for $50 million to fund its emergency operations in Yemen next year, more than double the $22 million it sought in 2011, she said.

The violence and civil unrest has had its toll on children, Kadi said. She said 138 children had been killed and hundreds wounded. Millions more are suffering psychologically from fear or being directly or indirectly witness to violence.

(Additional reporting by Tom Finn in Saada and Stephanie Nebehay in Geneva; Writing by Mahmoud Habboush)