The international human rights group also noted the re-election of President Omar al-Bashir would have no legal effect on the International Criminal Court charges pending against him. Al-Bashir is accused of war crimes and crimes against humanity for his alleged role in atrocities committed in Darfur.
In the April 11-15 national elections, independent observers reported logistical and administration problems, as well as instances of voter fraud such as multiple-voting and ballot-stuffing.
"Our concerns with these elections go beyond technical irregularities," Georgette Gagnon, Africa director at Human Rights Watch, said in a release. "Political oppression and human rights violations undermined the freedom and fairness of the vote all over Sudan."
The group alleges balloting was especially chaotic in the south, with serious irregularities reported in most states. Human Rights Watch said it found the National Congress Party-dominated government fostered a restrictive environment during the voting through harassment, intimidation, and arrests of activists, opposition members and election observers.
In addition to calling on Sudanese authorities to investigate the alleged abuses and bring anyone responsible to justice, Human Rights Watch urged international agencies and elections observers to monitor the post-elections situation closely should tensions rise over election results.
Regarding al-Bashir, Gagnon said the Sudanese leader "belongs in The Hague responding to the serious charges against him, for which victims have still seen no accountability.