German Chancellor Angela Merkel said the suicide attack in Damascus Wednesday that reportedly claimed the lives of top officials underlined the "urgent" need for a new UN resolution on Syria.

Merkel said after talks with Thai Prime Minister Yingluck Shinawatra that she was aware of reports that the blast claimed the lives of Syria's defence minister, General Daoud Rajha, and President Bashar al-Assad's brother-in-law.

"This shows that it is urgent that the next UN resolution be passed, on which all states in the international community should work so that the abuse of human rights stops and the political process can move forward," she said.

"You see that such a solution has not been possible. That is why I urge all those on the UN Security Council to agree on a joint resolution."

Syrian state television reported that Rajha and Assad's brother-in-law, deputy defence minister and former military intelligence chief Assef Shawkat, were killed in a suicide bomb attack targeting a meeting of top security chiefs.

The UN Security Council is expected to vote later Wednesday on a Western-backed resolution to consider sanctions if Assad's forces do not withdraw heavy weapons from Syrian cities within 10 days.

Syria's main ally Russia -- which has vowed to veto the resolution -- saw its own proposal rejected Tuesday by Britain, France, the United States, Germany and Portugal, diplomats said.