HEIDELBERG, Germany (Reuters) - German Chancellor Angela Merkel received two contrasting reactions to her immigration policy on Monday: a tearful thank-you from an Afghan boy, and a call from a party member for her to resign.

More than a million migrants have come to Germany since the start of 2015, and an initial outpouring of helpfulness has largely given way to caution and concerns about integration and security.

At a regional conference of Merkel's Christian Democrats (CDU), party member Ulrich Sauer urged Merkel - who said on Nov. 20 she wanted to run for a fourth term in next year's election - to resign.

"With your truly unparalleled 'laissez-faire' refugee policy you have burdened us with something that we will not get rid of any time soon," Sauer said. "Step down now before the damage you have done becomes even greater."

Moments later another CDU supporter, who helps refugees, introduced a young Afghan boy called Edris, whose father lifted him up so he could see Merkel.

"I would like to thank you, Mrs. Merkel," Edris said, speaking in German. "I am very, very happy."

Merkel praised him for having "learned a lot of German already" and urged him to keep practising.

When Edris said he wanted to touch the chancellor's hands, she walked over and Edris wiped away tears as they shook hands.

(Reporting by Reuters TV; Writing by Michelle Martin; Editing by Robin Pomeroy)