MANAGUA, Nicaragua (AP) — Nicaragua's national police denied a permit request Tuesday for a march to commemorate the one-year anniversary of the start of anti-government protests, setting up a possible conflict with the opposition, which has called for the march to go on.

The police said the request did not meet legal requirements. The opposition Blue and White National Unity coalition had sought the permit for a march Wednesday, but police said the two people who applied were involved in serious public disturbances in previous weeks.

Public demonstrations have been effectively banned for months.

Silvia Gutiérrez, spokeswoman for the opposition coalition, said the march would go on as planned Wednesday afternoon.

U.N. High Commissioner for Human Rights Michelle Bachelet urged the government to allow protests and "avoid repression." She expressed concern that "the protests organized for the coming days could trigger a violent reaction."

Protests began last April 18 over President Daniel Ortega's decree to cut social security benefits. Initial demonstrations by retirees were quickly joined by students as government supporters violently tried to put down the protests.

According to the Inter-American Commission on Human Rights, at least 325 people have been killed and 2,000 injured in the subsequent violence, while the U.N. Refugee Agency says more than 62,000 Nicaraguans have fled the country.

The opposition and the United States and European governments have called for Ortega to release those arrested in relation to the protests, approve electoral reforms and move up elections.

The government said Tuesday it released to home detention 636 prisoners who were detained "for various reasons," but it was unclear how many were political prisoners. In a brief statement, the interior ministry said the prisoners had been held in various facilities.

The number of prisoners is similar to that of those considered political prisoners by the opposition Civic Alliance. The government had agreed with the alliance to release the political prisoners during talks that stalled April 3. The freeing of those prisoners was supposed to be overseen by the International Committee of the Red Cross.

But Max Jerez, a member of the opposition's negotiating team, said the government had given them no advance warning of Tuesday's releases nor a list of those freed.

Lilliam Ruiz, a member of the Committee of Relatives of Political Prisoners, said that "fewer than 20" of the 636 prisoners released were people arrested for participating in the protests. She said the rest were regular prisoners.