Solved the issue by booting from a live USB (if you don’t have one, I recommend creating one) and then mounting the root partition.
After chrooting into it, install the kernel-install-mkinitcpio package and run the following command (in the chroot environment):
bootctl update
The command above might be unnecessary, anyways.
Now reinstall the Linux kernel:
pacman -S linux linux-headers
Exit the chroot environment and reboot the system.