* Al-Mahdi says to consider resuming talks with the government
* Sudan expects presidential and parliament votes in April (Adds Al-Mahdi's comments, supporters' celebrations)
By Khaled Abdel Aziz
KHARTOUM, June 15 (Reuters) - Sudanese authorities released opposition leader Sadiq al-Mahdi on Sunday, in a signal of the government's intent to ease political tensions ahead of elections next year.
Al-Mahdi, who was arrested in mid-May, was accused of undermining the constitution, a charge that could have led to the death penalty, after he said the government had committed violence against civilians in the Darfur region.
Sudan's State Minister of Information Yasser Youssef told Reuters that the release of al-Mahdi occurred within a "legal framework" but did not give further details.
Al-Mahdi, a former prime minister in Sudan's last elected civilian government, is the head of the Umma Party, the most prominent party opposing President Omar Hassan al-Bashir, who ousted him in 1989.
His arrest prompted weekly protests by his supporters. His Umma party cancelled national dialogue talks called by Bashir earlier this year to calm down opponents who have regularly been voicing discontent over the government's handling of the troubled western region of Darfur.
The head of the Congress Party, another opposition group, was arrested earlier this month after he too criticised violent practices by security forces in Darfur.
Speaking at his Umma Party headquarters in Khartoum after his release, Al-Mahdi said the party would "listen to opinions of all involved parties" before deciding whether to resume talks with the government which were halted after his arrest.
"Our position had always been to guard righteousness," added the popular leader who was held on the shoulders of supporters and cheered by hundreds who gathered to celebrate his return.
"The voice of Sadiq is the voice of the nation, the voice of hope," his supporters chanted.
Sudan is expected to hold presidential and parliamentary elections by April next year.
Bashir has been working to shore up his power in the face of an economic crisis since South Sudan seceded in 2011, taking with it three-quarters of the once unified nation's oil output.
He has remained in office for 25 years despite sporadic rebellions, U.S. trade sanctions, an attempted coup and an indictment from the International Criminal Court on charges of masterminding genocide and other war crimes in Darfur.
According to the United Nations statistics, up to 300,000 people were killed and two million others displaced during the 11-year conflict between the government and rebels in the Sudanese region of Darfur, 800 km west of Khartoum. (Reporting by Khalid Abdel Aziz in Khartoum; Writing by Yasmine Saleh; Editing by Dominic Evans and Stephen Powell)
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