State Department says Baquer Namazi and son Siamak let go due to medical needs after Tehran indicates freeing them supposed to lead to Washington unblocking $7 billion held abroad

Iranian state media reports funds held by South Korea due to American sanctions will be released following finalization of negotiations

Baquer Namazi, 85 and Siamak Namazi, 50, released by Iranian authorities in 'critical first steps' hailed by family lawyer who vows to keep fighting until both are back in US

Meeting joined by prisoners' families, former detainees of Islamic Republic, who call on US president not to link prisoners' fate to outcome of stalled nuclear talks

'Unless the president intervenes immediately, we are likely to languish in this abyss for the foreseeable future,' writes Siamak Namazi, Iranian-American detained since 2015

Babak Namazi says his father, 84-year-old Iranian-American Baquer Namazi, requires surgery within days to avoid a potentially catastrophic stroke

Families of Americans held by Tehran fear for loved ones' safety, believe prospects for release dimmed following US strike on Qassem Soleimani

Relatives speak of concerns that widespread economic discontent and recent rioting over fuel prices could impact their loved ones, demand that Tehran set them free

Zarif claims Tehran has not received response from Trump administration 6 months after raising possibility