Britain's deputy ambassador to the United Nations says Syria is carrying out a military offensive against its people that is “brutal and unwarranted,” but Syria rejected his remarks.

Philip Parham told reporters Wednesday that 2,000 mostly unarmed civilians have been killed in Syria, and some 3,000 have “forcibly disappeared.” He accused the Syrian regime of committing “gross” human rights violations, and said there will be no progress as long as security forces continue their operations against civilians.

He called for the use of force and mass arrests to stop immediately.

Parham spoke after the U.N. Security Council was briefed Wednesday on the situation in Syria by U.N. Assistant Secretary-General Oscar Fernandez-Taranco.

Syria's ambassador to the U.N., Bashar Ja'afari, called Parham's remarks inaccurate and misleading. He said Parham ignored important progress by Syrian officials, including meetings they have held with officials from other countries.

Syria's government widened its crackdown on dissidents Wednesday. At least 12 more people were killed.

Rights groups say at least 11 people died after security forces moved into the central city of Homs. They also say at least one civilian was killed after tanks moved into villages near the Turkish border.

Also Wednesday, The United States announced new sanctions on Syria, saying it would freeze U.S. assets of a bank and mobile phone operator. The White House reiterated that Syria would be “better off” without Mr. Assad.

Syrian President Bashar al-Assad is facing growing international condemnation for his crackdown on dissent. But he has defended the crackdown, saying it is a national duty to deal with what he called “outlaws” who block roads and, in his words, “terrorize” people.

On Wednesday, a delegation consisting of U.N. Security Council members India, Brazil and South Africa met with Syria's foreign minister . The group expressed “grave concern” about Syria's unrest and called for restraint and respect for human rights. The delegation said Mr. Assad assured them of his commitment to reforms and acknowledged that his security forces had made some mistakes in the initial stages of the unrest.

Last week, the Security Council strongly condemned Syria's crackdown on opposition protesters and called for the violence to stop.