WELLINGTON, New Zealand (AP) — Six months after a gunman killed 51 people at two Christchurch mosques, New Zealand's government is planning further restrictions to gun ownership. A bill introduced to Parliament on Friday would create a register to track all the guns in the country and require gun owners to renew their gun licenses every five years instead of every 10. It would also place new responsibilities on doctors to notify police if they believe a gun owner shouldn't have a license due to concerns over the owner's mental health. The government hopes lawmakers will approve the legislation by the end of the year. The proposed measures come after New Zealand in April rushed through legislation to ban assault weapons such as AR-15 style rifles. The government has launched a buyback scheme to compensate gun owners for the outlawed semi-automatics, and has so far collected about 19,000 weapons and 70,000 parts. The gun buyback and a parallel gun amnesty run until December. Prime Minister Jacinda Ardern told reporters in Christchurch the focus remained on preventing another attack like the one on March 15. She said the attack exposed weaknesses in gun laws, which the government was fixing. "We absolutely recognize there is a legitimate need in our communities to be able to access guns, particularly our rural community," Ardern said. "But what these changes do is recognize that actually there's a real responsibility that comes with gun ownership." Ardern has previously made the point that New Zealand has a different view on guns than the U.S., where gun ownership is seen as a constitutional right and is interpreted by many to be a defense against potential government overreach. "Owning a firearm is a privilege not a right," Ardern said on Friday. Brenton Tarrant, a 28-year-old Australian white supremacist, has pleaded not guilty to terrorism, murder and attempted murder charges following the March attacks. He remains in jail ahead of his trial. The judge in the case this week agreed to a request by prosecutors to delay the start of the trial by a month until next June to avoid a clash with the Islamic holy month of Ramadan. Judge Cameron Mander noted that many of the witnesses are Muslim and that defense lawyers hadn't raised any objections to the delay.