MADRID (Reuters) - The parents of Madeleine McCann, the 4-year-old snatched from her Portuguese holiday apartment almost a month ago, appealed for Spanish police on Friday to actively investigate their daughter's disappearance.

"I would like some reassurance in Spain that there has been some pro-active investigation regarding Madeleine's disappearance," Gerry McCann told a news conference in Madrid.

McCann said police needed to investigate the possibility that Madeleine's disappearance and that of other children in Portugal and Spain were connected. Spanish police are investigating the disappearance of 7-year-old Yeremi Vargas, from his home island of Gran Canaria on March 10.

"I think it is at least worth exploring the possibility that Madeleine's disappearance should not be considered in isolation, putting it into context with any other child's disappearance, abduction through the Iberian peninsula and possibly the Canary Islands as well," he said.

During their trip to Madrid, the McCanns will meet Spanish Interior Minister Alfredo Rubalcaba and child welfare groups. Police officials were not immediately reachable for comment on what Spain had done to find Madeleine.

She was snatched on May 3 as her parents ate at a nearby restaurant in the Portuguese resort of Praia da Luz, which is slightly more than 100 km from the Spanish border.

"We are here to ask the Spanish public for help. We feel it is possible that Madeleine was moved from Portugal to Spain although we are not certain of that," McCann said.