Medical officials in Yemen say government security forces have killed at least 20 people in clashes with anti-government protesters, a day after the city saw its worst violence in several months.

Pro-government snipers fired from rooftops in the center of the city Monday, while troops clashed with protesters in another part of the city.

The officials said the dead include a child and at least three soldiers who defected.

Sunday, security forces killed at least 26 people and wounded hundreds when they fired on tens of thousands of protesters. The demonstrators were marching toward the presidential palace from nearby Change Square, where thousands of protesters have been camped out for months demanding President Ali Abdullah Saleh step down.

The government said Monday it expresses “sorrow and condemnation” for acts of violence such as those that took place in the capital on Sunday. Foreign Minister Abu Bakr al-Kurbi told the U.N. Human Rights Council the government will investigate and hold accountable those responsible for the violence.

The youth-led protest movement in Yemen has stepped up demonstrations in the past week, angry after Mr. Saleh instructed his deputy to negotiate a power-sharing deal. Many call the move the latest of the president's delaying tactics.

Mr. Saleh remains in Saudi Arabia, where he has been recovering from injuries sustained in a June attack on his presidential compound.

In April, the six-nation Gulf Cooperation Council proposed a plan designed to end Yemen's government turmoil. Mr. Saleh agreed to the proposal three times, but backed out each time before the deal could be signed.