A banned Marxist group in Turkey says it carried out Tuesday's suicide bombing in Istanbul in which the female bomber and a policeman died.
The DHKP-C said on its website "our sacrificial fighter... carried out the sacrificial action on the tourist police department in Sultanahmet".
Last week the group claimed an Istanbul attack in which a man was arrested after throwing grenades at police. Nobody was injured in the incident.
DHKP-C says it is fighting corruption.
The group accused the state of protecting "corrupt" ministers loyal to President Recep Tayyip Erdogan, whose Islamist-rooted AK Party dominates Turkish politics.
In Tuesday's bombing a woman targeted a police station in the tourist hub of Sultanahmet, near the Blue Mosque and Hagia Sophia museum.
She spoke English with "a thick accent", but her nationality and identity remained unknown, Istanbul governor Vasip Sahin told Turkish TV. A second policeman was injured in the attack.
The Turkish Hurriyet news website has named her, but there is no official confirmation.
The BBC's Mark Lowen in Istanbul says the claim of responsibility is credible.
Mark Lowen, BBC correspondent in Istanbul:
The shadowy Revolutionary People's Liberation Front, or DKHP-C, has grown over the past 30 years.
Marxist in ideology, it is a home-grown organisation, fiercely anti-Western, and has frequently targeted military and political figures in Turkey, hitting out at what it calls "imperialist control" of the country.
In the 1980s and 1990s it focused on assassinations. From the 2000s, it added suicide bombings to its repertoire, hitting police and, in 2013, the US embassy in Ankara.
It is not the only domestic group here with the "terrorist" label. Most notably the Kurdistan Workers' Party (PKK), which rose during the same period as DKHP-C, resorted to a campaign of bombings and assassinations, striving for a Kurdish state or greater autonomy within Turkey and an end to the repression of Kurds.
The two organisations are not linked, though their similar tactics reveal the depth of the security challenges Turkey continues to face.
The DHKP-C statement said the motive was to protest at government corruption and avenge the death of a boy fatally injured by police.
Berkin Elvan, 15, died last year from injuries sustained in anti-government protests in 2013.
The statement referred to an AK Party-dominated parliamentary committee which voted on Monday not to send for trial four ministers accused of corruption.
"The state that protects those who killed Berkin and those corrupt ministers is the same," it said.
The Turkish state was based on "corruption, blood, exploitation and pillage", it said, adding: "we will demolish this order!"
Last week's attack was on guards outside Dolmabahce Palace, near Prime Minister Ahmet Davutoglu's offices. He is believed to have been absent when it happened.
The radical left-wing, anti-Nato group has launched attacks since the 1980s. Turkey and its Western allies consider it a "terrorist" group.
Governor Sahin said the woman bomber, dressed in a niqab, entered the Sultanahmet police station and told officers she had lost her wallet before detonating the bomb.
It comes at a time of increased tension in Turkey, following clashes between security forces and Kurds in the south-east, fuelled by the Kurdish battle against Islamists in northern Syria.
In recent years attention has focused mainly on Turkey's long-running conflict with the rebel Kurdistan Workers' Party (PKK), which wants self-rule for the Kurds.