BAGHDAD, April 28 Iraq formed its first democratically-elected government in more than 50 years on Thursday, ending three months of political stalemate that has crippled efforts to tackle violence. But Prime Minister Ibrahim al-Jaafari failed to name permanent ministers to five key portfolios, including oil and Defence, and a top Sunni Muslim official criticised the new government as sectarian.

The 275-seat parliament voted overwhelmingly in favour of the cabinet proposed by Jaafari, ending a power vacuum that had dissipated the optimism created by the Jan. 30 elections.

The government’s formation coincided with the 68th birthday of former dictator Saddam Hussein, who is awaiting trial in a US-run jail on Baghdad’s outskirts.

‘‘The journey was full of blood, words, sweat and tears until this day, when our people gave you their trust to carry out this responsibility,’’ Jaafari told Parliament ahead of the vote.

The Cabinet, designed to accommodate Iraq’s rival ethnic and sectarian groups, will consist of 31 ministers and four deputy prime ministers, as well as Jaafari.

Most of the posts went to majority Shia Muslims, who have gained power after decades of Sunni-led rule under Saddam. Kurds and Sunni Arabs were also strongly represented. No permanent ministers were named for the oil, defence, electricity, industry and human rights portfolios, while two deputy prime minister posts were left vacant. Jaafari will be acting Defence minister and Ahmad Chalabi acting oil minister. Seven ministries went to women.

Vice President Ghazi al-Yawar, a Sunni, said the line-up was a sectarian carve-up. ‘‘We’re not happy, but we have to wait until all the nominations are permanent before we do anything.’’

Sunnis have few seats in Parliament after most of them boycotted the election or stayed away fearing violence.

Chalabi’s appointment to the crucial oil ministry is likely to be unpopular with many Iraqis, who polls show have little love for the former exile Shia once close to the Pentagon. Chalabi promised no abrupt changes at the ministry. ‘‘My focus will be stability,’’ he told Reuters.

The interior ministry went to Bayan Jabbor, a Shia.

Some US and Iraqi officials have warned against any purge of Sunnis, currently central to the fight against insurgents, from the interior ministry. Jaafari, an Islamist Shia, said he hoped to put permanent ministers in place within a few days and was at pains to insist the spread reflected a government of ‘national unity’.

But some Iraqis were sceptical.

‘‘Forming a government is an important step. But I am pessimistic,’’ said Nasr Saeed, 37, a construction company employee. ‘‘It’s not a government of national unity but sectarian and racist.’’

Yawar warned that Sunnis would not accept any candidate being imposed on them in the final allocation of portfolios. ‘‘The Sunnis will not accept any name being imposed on them,even if it is the name of a Sunni,’’ he said, referring to the defence ministry, which was expected to go to a Sunni.

No members of Iyad Allawi’s party were included. Talks with the former prime minister, a secular Shia, broke down this week after he was said to have demanded too many cabinet posts. Allawi’s party came third in the elections, winning 40 seats in parliament, and will now go into opposition.