Geneva, June 19 (IANS): UN Special Envoy to Yemen Ismail Ould Cheikh Ahmed strongly condemned on Friday the terrorist attacks that took place in Yemen's capital Sanaa earlier this week, and deeply regretted the civilian casualties.

At least four people were killed on Wednesday and 50 others wounded in a series of car-bomb attacks, for which Yemen's Islamic State (IS) branch claimed the responsibility.

In a statement on Friday, Ould Cheikh Ahmed expressed his condolences to the victims' families and friends, Efe news agency reported.

"These criminal acts cannot be justified under any circumstances, and I call for those responsible to claim their responsibility," he said.

The envoy urged all political, religious and military parties along with community leaders to do everything necessary to prevent attacks on religious centres and other civil institutions.

Ould Cheikh Ahmed asked those parties to actively and positively participate in the peace talks, which have been taking place this week in Geneva.

Over the last three days, the UN official met with both representatives from the Houthi rebel delegation and President Abd Rabbu Mansour Hadi, living in exile in Saudi Arabia, to try to convince them to come to the table.

According to the UN, the hostilities in Yemen have killed more than 2,600 people, half of whom were civilians, and left one million people internally displaced. Twenty million of the total 25 million Yemenis are in dire need of humanitarian assistance.