The Kremlin has announced that Vladislav Surkov, considered the architect of modern Russia's tightly controlled political system, resigned his post of deputy prime minister.

The resignation of the longtime Kremlin strategist followed a public feud with investigators over a criminal probe into Skolkovo, a government project to promote innovation modelled on Silicon Valley and overseen by Surkov.

The Kremlin said in a written statement on Wednesday that Surkov, 48, had left his post voluntarily, but analysts said the former Kremlin "grey cardinal" was forced out amid a growing rift between Putin's Kremlin and the government.

Prime Minister Dmitry Medvedev's spokeswoman Natalia Timakova said that Surkov tendered his resignation on April 26.

His departure comes amid what observers describe as signs of growing infighting among Kremlin elites during Putin's third term and the probe into the high-tech fund backed by Surkov.

Putin poll promises

Dmitry Peskov, a spokesman for Russian President Vladimir Putin, said that Surkov's departure was not related to the investigation at the Skolkovo fund and that he quit over the government's poor implementation of Putin's election promises.

"It is related to the priority topic and the high-priority task of implementing presidential decrees," Peskov told Kommersant FM radio.

Surkov declined to comment on his resignation.

He  was dismissed from the post of first deputy Kremlin chief of staff in a shake-up in December 2011 that was seen as the Kremlin's reaction to huge opposition protests that winter.

Surkov had worked in the Kremlin administration from 1999 and oversaw Putin's domestic political strategy, political parties in parliament, electoral campaigns and the tightly controlled media.

He was appointed first deputy prime minister in 2011 but was essentially sidelined, analysts said.

Source: Agencies