  The first high-energy neutrino source identified by IceCube was a blazar - an
active galactic nucleus driving a relativistic jet towards Earth. Jets driven
by accreting black holes are commonly assumed to be needed for high-energy
neutrino production. Recently, IceCube discovered neutrinos from Seyfert
galaxies, which appears unrelated to jet activity. Here, we show that the
observed luminosity ratios of neutrinos and hard X-rays from blazars TXS
0506+056 and GB6 J1542+6129 are consistent with neutrino production in a
$\gamma$-obscured region near a central supermassive black hole, with the X-ray
flux corresponding to reprocessed $\gamma$-ray emission with flux comparable to
that of neutrinos. Similar neutrino - hard X-ray flux ratios are found for four
Seyfert galaxies, NGC 1068, NGC 4151, CGCG 420-015 and NGC 3079, raising the
possibility of a common neutrino production mechanism that may not involve a
strong jet.
