– German politicians have called on domestic intelligence officials to place the nationalist Alternative for Germany party under surveillance on suspicion of undermining the country's constitution, as it stokes resentments against immigrants and Chancellor Angela Merkel's immigration policies.

The call came from members of the Social Democrats, part of the governing coalition, as well as the opposition Greens and some members of Merkel's own Christian Democrats.

There had been previous demands for surveillance of Alternative for Germany, but they grew in recent days after images spread of leading party members marching beside supporters of the anti-Islam Pegida movement in the eastern city of Chemnitz. A party leader also expressed support for violent demonstrations there after two immigrants were arrested in the fatal stabbing of a German man.

Horst Seehofer, Germany's highest security official, rejected the calls, saying he did not see sufficient grounds for monitoring the party. Political parties, their associated organizations and individual politicians can be subject to such measures if authorities can establish clear evidence of efforts to undermine the principles of the country's constitution.

The political debate came amid more anger Monday over the sentencing of a young migrant, believed to be from Afghanistan, to 8 ½ years in prison for killing his 15-year-old German ex-girlfriend, in a case that became a flash point for fears over immigration. Many people, particularly those on the anti-immigrant right, condemned the penalty as too lenient.

Because German authorities were not able to establish the defendant's identity definitively, and he claimed to be 15 at the time of the crime, he was tried as a juvenile, so the maximum sentence was 10 years.

The killing, in December 2017, took place in daylight in a drugstore in Kandel, a small western German town.

Prosecutors argued that the killer had been jealous after his victim broke up with him several weeks earlier. In keeping with German privacy law, he was identified only as Abdul D., and she as Mia V.

Volker Poss, the mayor of Kandel, said right-wing groups were organizing demonstrations in the town for later Monday, to protest what they considered an overly lenient sentence for the killing.