Sudanese President Omar Hassan Al-Bashir, wanted for war crimes by the International Criminal Court (ICC), was sworn in on Thursday after his re-election in voting marred by boycotts.

Bashir, who rejects charges of ordering mass murder, rape and torture in western Darfur, is due to preside over a January referendum on secession for south Sudan, which many analysts believe will bring the oil-producing region independence.

Wearing a flowing white robe and white headdress, Bashir welcomed heads of at least five African states attending the ceremony, including Mauritania, Chad and Djibouti.

'This phase will mark a fresh start,' Bashir told a packed parliament hall. 'No return to war, and there will be no place for undermining security and stability,' he said.

But the pomp and circumstance honouring the controversial leader, especially as tensions persist between Khartoum and the semi-autonomous south and fighting continues in Darfur, put European diplomats and UN officials in a quandary.

The EU supports ICC efforts to bring Bashir to justice but is also keen to maintain dialogue to ensure the referendum does not trigger a renewal of Sudan's decades-long civil war.

The United Nations said it would send its top two diplomats in Sudan despite criticism from human rights advocates.

'Diplomats attending Al-Bashir's inaugural would be making a mockery of their governments' support for international justice,' said Elise Keppler, International Justice Program senior counsel at US-based Human Rights Watch.

Bashir's swearing-in follows his easy victory in an April election -- he won 68 percent of the vote -- that was marked by opposition boycotts and allegations of widespread fraud.

Bashir's party and allies also won around 95 percent of parliamentary seats in the north, giving them more than the required two-thirds majority to make constitutional changes.

The former southern rebel Sudan People's Liberation Movement (SPLM) won most of the southern seats, around 20 percent of the total parliament. South Sudan President and SPLM leader Salva Kiir, who appeared at the inauguration in his trademark giant cowboy hat, is in talks to form a government with Bashir.

Bashir, who took power in a 1989 coup, was last sworn in after a north-south peace deal in 2005 that ended Africa's longest civil war, a conflict that claimed some 2 million lives and destabilised much of the region. - Reuters