Wichita ? Three Wichita-based anti-abortion groups say they have received death threats in response to last month’s killing of abortion provider George Tiller.

For years, Operation Rescue has received threats, but the number increased dramatically after Tiller’s killing, the group’s president, Troy Newman, said Thursday.

Some of the threats have been aimed at anti-abortion activities planned in Wichita this weekend, Newman said.

Soon after Tiller’s shooting, police contacted four to five local anti-abortion groups, asking them to contact authorities if they received threats, said Wichita police Capt. Brent Allred.

For this weekend’s events, off-duty officers have been hired to help provide security, Newman said. It wasn’t clear Thursday whether on-duty officers will be deployed.