SANAA (AFP) - Al-Qaeda claimed on Saturday that its militants killed dozens of Shi'ite rebels in Yemen and tried to assassinate the US ambassador, as a new government was announced in the strife-torn country.

The Cabinet was formed on Friday shortly before the UN Security Council slapped sanctions against influential former president Ali Abdullah Saleh and two rebel commanders for threatening peace.

In apparent retaliation on Saturday, Saleh's General People's Congress party sacked from its leadership Yemeni President Abdrabuh Mansur Hadi, following accusations he solicited the sanctions.

Yemen has been dogged by instability since an Arab Spring-inspired uprising forced Saleh from power in February 2012, and the Shi'ite Huthi rebels and Al-Qaeda have sought to step into the power vacuum.

In the latest violence, Al-Qaeda claimed twin attacks early on Saturday that it said killed "dozens" of Huthis in the central region of Rada, where the Sunni Muslim militants have halted a rapid territorial advance by their Shi'ite rivals.

The turmoil has raised fears that the Arabian Peninsula nation, which neighbours oil-flush Saudi Arabia and lies on the key shipping route from the Suez Canal to the Gulf, may become a failed state.

Al-Qaeda also said it had tried to kill the US ambassador to Yemen, Matthew Tueller, but the two bombs were detected "minutes before their detonation".

The devices were planted on Thursday outside the house of President Abdrabuh Mansur Hadi, the media arm of Al-Qaeda's Yemen branch said in a statement on Twitter.

There was no official confirmation of the failed plot.

Washington, which sees Hadi as a key ally in the fight against Al-Qaeda, welcomed the launch of the new 36-member Cabinet.

"This multi-party Cabinet must represent the strength of Yemeni unity over individual and partisan interests that may seek to derail the goals of a nation," US National Security Council spokeswoman Bernadette Meehan said.

The new government was formed as part of a UN-brokered peace deal under which the Huthis are supposed to withdraw from the capital Sanaa, which they seized control of in September.

Though the Huthis, who are also known as Ansarullah, are not directly represented in the new government, six of its members are considered close to the insurgents.

On Nov 1, the main parties signed an agreement brokered by UN envoy to Yemen Jamal Benomar for the formation of a government of technocrats.

Under the accord, representatives of the rebels and their rivals, the Sunni Al-Islah (Reform) Islamic party, mandated Hadi to form a government and committed to support it.

In the wake of the new agreement, Benomar warned in an interview with AFP that without the rapid formation of a government, tensions between Shi'ites and Sunnis were likely to increase, sinking the country deeper into crisis.

Al-Qaeda said on Saturday it had launched two attacks against Huthi posts in Rada.

"Dozens of Huthis were killed and wounded," it said, when a militant rammed his explosives-laden car into a medical centre converted by Huthis into a barracks, in the region of Manaseh.

It was not immediately possible to verify the report.

In another attack, Al-Qaeda militants opened fire on a school occupied by rebels in Jarrah valley, also near Rada, tribal sources and the militant group said.

An Al-Qaeda statement posted online said four militants stormed the building.

On Friday, the UN Security Council slapped a US-proposed visa ban and assets freeze on him and two allied Shi'ite rebel commanders for threatening peace in the impoverished country.

The Huthis are widely thought to be backed by Saleh.

Washington said Saleh "was behind the attempts to cause chaos throughout Yemen" by using the Huthis to weaken the government and "create enough instability to stage a coup".

On Friday, Saleh supporters had protested alongside rebels denouncing the planned sanctions.

The top UN body in August called on the Huthis to end their armed uprising and warned of sanctions against those who threaten the stability of Yemen.